Organometallic complex, light-emitting element, light-emitting device, electronic device, and lighting device

ABSTRACT

Provided is an organometallic complex which emits light with a short wavelength and has high emission efficiency and high heat resistance. The organometallic complex includes a central metal; and a first ligand, a second ligand, a third ligand, and a fourth ligand which are coordinated to the central metal. The first ligand includes a triazole skeleton including nitrogen bonded to the central metal. The second ligand includes an indolo[3,2-b]carbazole skeleton whose 6-position is bonded to the central metal or a pyrido[2,3-b:6,5-b′]diindole skeleton whose 6-position is bonded to the central metal. The third ligand includes a benzene skeleton whose carbon is bonded to the central metal. The fourth ligand includes a pyridine skeleton whose nitrogen is bonded to the central metal or a benzene skeleton whose carbon is bonded to the central metal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to an organometalliccomplex, particularly, to an organometallic complex that is capable ofconverting triplet excitation energy into light emission. In addition,one embodiment of the present invention relates to a light-emittingelement, a light-emitting device, an electronic device, and a lightingdevice each including the organometallic complex. Note that oneembodiment of the present invention is not limited to the abovetechnical field. The technical field of one embodiment of the inventiondisclosed in this specification and the like relates to an object, amethod, or a manufacturing method. In addition, one embodiment of thepresent invention relates to a process, a machine, manufacture, or acomposition of matter. Specifically, examples of the technical field ofone embodiment of the present invention disclosed in this specificationinclude a semiconductor device, a display device, a liquid crystaldisplay device, a light-emitting device, a power storage device, amemory device, a method of driving any of them, and a method ofmanufacturing any of them.

2. Description of the Related Art

A light-emitting element having a structure in which an organic compoundthat is a light-emitting substance is provided between a pair ofelectrodes (also referred to as an organic EL element) has attractedattention as a next-generation flat panel display in terms ofcharacteristics such as being thin and light in weight, high-speedresponse, and low voltage driving. When a voltage is applied to thisorganic EL element (light-emitting element), electrons and holesinjected from the electrodes recombine to put the light-emittingsubstance into an excited state, and then light is emitted in returningfrom the excited state to the ground state. The excited state can be asinglet excited state (S*) and a triplet excited state (T*). Lightemission from a singlet excited state is referred to as fluorescence,and light emission from a triplet excited state is referred to asphosphorescence. The statistical generation ratio thereof in thelight-emitting element is considered to be S*:T*=1:3.

Among the above light-emitting substances, a compound capable ofconverting singlet excitation energy into light emission is called afluorescent compound (fluorescent material), and a compound capable ofconverting triplet excitation energy into light emission is called aphosphorescent compound (phosphorescent material).

Accordingly, the internal quantum efficiency (the ratio of the number ofgenerated photons to the number of injected carriers) of alight-emitting element including a fluorescent material is thought tohave a theoretical limit of 25%, on the basis of S*:T*=1:3, while theinternal quantum efficiency of a light-emitting element including aphosphorescent material is thought to have a theoretical limit of 75%.

In other words, a light-emitting element including a phosphorescentmaterial has higher efficiency than a light-emitting element including afluorescent material. Thus, various kinds of phosphorescent materialshave been actively developed in recent years. An organometallic complexthat contains iridium or the like as a central metal is particularlyattracting attention because of its high phosphorescence quantum yield(for example, see Patent Document 1).

REFERENCE Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2009-023938

SUMMARY OF THE INVENTION

Although phosphorescent materials exhibiting excellent characteristicshave been actively developed as disclosed in Patent Document 1,development of novel materials with better characteristics has beendesired.

In view of the above, according to one embodiment of the presentinvention, a novel organometallic complex is provided. In particular, anovel organometallic complex emitting light with a short wavelength,which is a phosphorescent material that has been especially desired tobe developed, is provided. According to one embodiment of the presentinvention, a novel organometallic complex with a high emission quantumefficiency is provided. According to one embodiment of the presentinvention, a novel organometallic complex which achieves improved colorpurity by a reduction of half width of an emission spectrum is provided.Furthermore, a novel organometallic complex with an excellentsublimation property is provided. According to one embodiment of thepresent invention, a novel organometallic complex that can be used in alight-emitting element is provided. According to one embodiment of thepresent invention, a novel organometallic complex that can be used in anEL layer of a light-emitting element is provided. According to oneembodiment of the present invention, a novel light-emitting element isprovided. In addition, according to one embodiment of the presentinvention, a novel light-emitting device, a novel electronic device, ora novel lighting device is provided. Note that the descriptions of theseobjects do not disturb the existence of other objects. In one embodimentof the present invention, there is no need to achieve all the objects.Other objects will be apparent from and can be derived from thedescription of the specification, the drawings, the claims, and thelike.

One embodiment of the present invention is an organometallic complexincluding a central metal; and a first ligand, a second ligand, a thirdligand, and a fourth ligand which are coordinated to the central metal.The first ligand includes a triazole skeleton including nitrogen bondedto the central metal. The second ligand includes anindolo[3,2-b]carbazole skeleton whose 6-position is bonded to thecentral metal or a pyrido[2,3-b:6,5-b′]diindole skeleton whose6-position is bonded to the central metal. The third ligand includes abenzene skeleton whose carbon is bonded to the central metal. The fourthligand includes a pyridine skeleton whose nitrogen is bonded to thecentral metal or a benzene skeleton whose carbon is bonded to thecentral metal.

Another embodiment of the present invention is an organometallic complexrepresented by a general formula (G1) below.

In the general formula (G1), M represents Pt or Pd. Each of R¹ to R¹⁶independently represents any of hydrogen, an alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted aryl group having 6 to13 carbon atoms. One of Q¹ and Q² represents nitrogen, and the otherthereof represents carbon. Furthermore, a ring A represents a triazolering.

Another embodiment of the present invention is an organometallic complexrepresented by a general formula (G1-1) or a general formula (G1-2)below.

Note that in the general formula (G1-1) or the general formula (G1-2), Mrepresents Pt or Pd. Each of R¹ to R¹⁶ independently represents any ofhydrogen, an alkyl group having 1 to 6 carbon atoms, and a substitutedor unsubstituted aryl group having 6 to 13 carbon atoms. Furthermore, aring A represents a triazole ring.

When the ring A is represented by the general formula (α) below in eachof the above general formula (G1), the above general formula (G1-1), andthe above general formula (G1-2), the general formula (α) is any one ofthe structural formula (α-1), the structural formula (α-2), thestructural formula (α-3), and the structural formula (α-4) below.

Note that in each of the general formulae (α-1), (α-2), (α-3), and(α-4), each of R²¹ to R²⁸ independently represents any of hydrogen, analkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted aryl group having 6 to 13 carbon atoms.

Since, in each of the above organometallic complexes which areembodiments of the present invention, one of four types of ligandscoordinated to the central metal includes a triazole skeleton includingnitrogen bonded to the central metal, energy can be efficientlyabsorbed, and phosphorescence having an emission spectrum with a peak ataround 500 nm can be obtained with high emission quantum efficiency. Inthe four types of ligands coordinated to the central metal, anindolo[3,2-b]carbazole skeleton whose 6-position is bonded to thecentral metal or a pyrido[2,3-b:6,5-b′]diindole skeleton whose6-position is bonded to the central metal; a benzene skeleton whosecarbon is bonded to the central metal; and a pyridine skeleton whosenitrogen is bonded to the central metal or a benzene skeleton whosecarbon is bonded to the central metal are bonded to one another throughnitrogen of an indolo[3,2-b]carbazole skeleton whose 6-position isbonded to the central metal or a pyrido[2,3-b:6,5-b′]diindole skeletonwhose 6-position is bonded to the central metal, and therefore, theabove-described organometallic complex which is one embodiment of thepresent invention has a rigid structure. Thus, the molecular structureis stabilized and less likely to be distorted, and therefore, the heatresistance can be improved, and the oscillator strength of electrontransition between the lowest vibrational levels (0-0 transition) inwhich transition energy of absorption is equal to that of light emissionis increased because a difference between the bond length of atoms in aground state and the bond length of atoms in an excited state isextremely small, so that an emission spectrum can be further narrowed,and phosphorescence with high color purity can be obtained.

Another embodiment of the present invention is an organometallic complexrepresented by the structural formula (100) below.

The organometallic complex which is one embodiment of the presentinvention is very effective for the following reason: the organometalliccomplex can emit phosphorescence, that is, it can provide luminescencefrom a triplet excited state and can exhibit light emission, andtherefore higher efficiency is possible when the organometallic complexis used in a light-emitting element. Thus, one embodiment of the presentinvention also includes a light-emitting element in which theorganometallic complex of one embodiment of the present invention isused.

One embodiment of the present invention includes, in its scope, not onlya light-emitting device including the light-emitting element but also alighting device including the light-emitting device. The light-emittingdevice in this specification refers to an image display device and alight source (e.g., a lighting device). In addition, the light-emittingdevice includes, in its category, all of a module in which a connectorsuch as a flexible printed circuit (FPC) or a tape carrier package (TCP)is connected to a light-emitting device, a module in which a printedwiring board is provided on the tip of a TCP, and a module in which anintegrated circuit (IC) is directly mounted on a light-emitting elementby a chip on glass (COG) method.

According to one embodiment of the present invention, a novelorganometallic complex can be provided. In particular, a novelorganometallic complex emitting light with a short wavelength can beprovided. In addition, a novel organometallic complex with a highemission quantum efficiency can be provided. Furthermore, anorganometallic complex which achieves improved color purity by areduction of half width of an emission spectrum can be provided.Furthermore, a novel organometallic complex with an excellentsublimation property can be provided. According to one embodiment of thepresent invention, a novel organometallic complex that can be used in alight-emitting element can be provided. According to one embodiment ofthe present invention, a novel organometallic complex that can be usedin an EL layer of a light-emitting element can be provided. Note that anew light-emitting element including the novel organometallic complexcan be provided. Furthermore, a novel light-emitting device, a novelelectronic device, or a novel lighting device can be provided. Note thatthe description of these effects does not disturb the existence of othereffects. One embodiment of the present invention does not necessarilyachieve all the effects listed above. Other effects will be apparentfrom and can be derived from the description of the specification, thedrawings, the claims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B each illustrate a structure of a light-emitting element.

FIGS. 2A and 2B each illustrate a structure of a light-emitting element.

FIGS. 3A to 3C illustrate a light-emitting device.

FIGS. 4A and 4B illustrate a light-emitting device.

FIGS. 5A to 5E-1 and 5E-2 illustrate electronic devices.

FIGS. 6A to 6C illustrate an electronic device.

FIGS. 7A and 7B illustrate an automobile.

FIGS. 8A to 8D illustrates lighting devices.

FIG. 9 illustrates lighting devices.

FIGS. 10A and 10B illustrate an example of a touch panel.

FIGS. 11A and 11B each illustrate an example of a touch panel.

FIGS. 12A and 12B each illustrate an example of a touch panel.

FIGS. 13A and 13B are a block diagram and a timing chart of a touchsensor.

FIG. 14 is a circuit diagram of a touch sensor.

FIG. 15 is a ¹H-NMR chart of an organometallic complex represented bythe structural formula (100).

FIGS. 16A and 16B are graphs showing the ultraviolet-visible absorptionspectrum and the emission spectrum of the organometallic complexrepresented by the structural formula (100).

FIG. 17 shows LC/MS analysis results of the organometallic complexrepresented by the structural formula (100).

FIG. 18 illustrates a structure of a light-emitting element.

FIG. 19 shows current density-luminance characteristics ofLight-emitting Element 1.

FIG. 20 shows voltage-luminance characteristics of Light-emittingElement 1.

FIG. 21 shows luminance-current efficiency characteristics ofLight-emitting Element 1.

FIG. 22 shows voltage-current characteristics of Light-emitting Element1.

FIG. 23 shows chromaticity coordinates of Light-emitting Element 1.

FIG. 24 shows an emission spectrum of Light-emitting Element 1.

FIG. 25 shows current density-luminance characteristics ofLight-emitting Element 2.

FIG. 26 shows voltage-luminance characteristics of Light-emittingElement 2.

FIG. 27 shows luminance-current efficiency characteristics ofLight-emitting Element 2.

FIG. 28 shows voltage-current characteristics of Light-emitting Element2.

FIG. 29 shows chromaticity coordinates of Light-emitting Element 2.

FIG. 30 shows an emission spectrum of Light-emitting Element 2.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. Note that the present inventionis not limited to the following description, and modes and detailsthereof can be variously modified without departing from the spirit andscope of the present invention. Therefore, the present invention shouldnot be construed as being limited to the description in the followingembodiments.

Note that the terms “film” and “layer” can be interchanged with eachother according to circumstances. For example, in some cases, the term“conductive film” can be used instead of the term “conductive layer,”and the term “insulating layer” can be used instead of the term“insulating film.”

(Embodiment 1)

In this embodiment, organometallic complexes which are embodiments ofthe present invention will be described.

Each of the organometallic complexes which are described in thisembodiment includes a central metal and four types of ligandscoordinated to the central metal. The first ligand of the four types ofligands includes a triazole skeleton including nitrogen bonded to thecentral metal. The second ligand of the four types of ligands includesan indolo[3,2-b]carbazole skeleton whose 6-position is bonded to thecentral metal or a pyrido[2,3-b:6,5-b′]diindole skeleton whose6-position is bonded to the central metal. The third ligand of the fourtypes of ligands includes a benzene skeleton whose carbon is bonded tothe central metal. The fourth ligand of the four types of ligandsincludes a pyridine skeleton whose nitrogen is bonded to the centralmetal or a benzene skeleton whose carbon is bonded to the central metal.

In the general formula (G1), M represents Pt or Pd. Each of R¹ to R¹⁶independently represents any of hydrogen, an alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted aryl group having 6 to13 carbon atoms. One of Q¹ and Q² represents nitrogen, and the otherthereof represents carbon. Furthermore, a ring A represents a triazolering.

Note that in the case where Q¹ is nitrogen and Q² is carbon in the abovegeneral formula (G1), an organometallic complex of one embodiment of thepresent invention is represented by the general formula (G1-1) below. Inthe case where Q¹ is carbon and Q² is nitrogen in the above generalformula (G1), an organometallic complex of one embodiment of the presentinvention is represented by the general formula (G1-2) below.

Note that in each of the general formulae (G1-1) and (G1-2), Mrepresents Pt or Pd. Each of R¹ to R¹⁶ independently represents any ofhydrogen, an alkyl group having 1 to 6 carbon atoms, and a substitutedor unsubstituted aryl group having 6 to 13 carbon atoms. Furthermore, aring A represents a triazole ring.

In each of the above general formulae (G1), (G1-1), and (G1-2), the ringA is a triazole ring represented by the general formula (α), and asspecific examples thereof, structures represented by the generalformulae (α-1), (α-2), (α-3), and (α-4) below can be given.

Note that in each of the above general formulae (α-1), (α-2), (α-3), and(α-4), each of R²¹ to R²⁸ independently represents any of hydrogen, analkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted aryl group having 6 to 13 carbon atoms.

Specific examples of the alkyl group having 1 to 6 carbon atoms in theabove general formulae (G1), (G1-1), and (G1-2) and the above generalformulae (α-1), (α-2), (α-3), and (α-4) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentylgroup, a 1-methylpentyl group, a hexyl group, an isohexyl group, asec-hexyl group, a tert-hexyl group, a neohexyl group, a 3-methylpentylgroup, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutylgroup, and a 2,3-dimethylbutyl group.

Specific examples of the substituted or unsubstituted aryl group having6 to 13 carbon atoms in the above general formulae (G1), (G1-1), and(G1-2) and the above general formulae (α-1), (α-2), (α-3), and (α-4)include a phenyl group, a tolyl group (an o-tolyl group, an m-tolylgroup, and a p-tolyl group), a naphthyl group (a 1-naphthyl group and a2-naphthyl group), a biphenyl group (a biphenyl-2-yl group, abiphenyl-3-yl group, and a biphenyl-4-yl group), a xylyl group, anindenyl group, a fluorenyl group, a phenanthryl group, and an indenylgroup. For example, in the case where the aryl group is a 2-fluorenylgroup having two phenyl groups at the 9-position as a substituent, thephenyl groups may be bonded to each other to become aspiro-9,9′-bifluoren-2-yl group.

Since, in each of the organometallic complexes which are embodiments ofthe present, invention and represented by the above general formulae(G1), (G1-1), and (G1-2), one of four types of ligands coordinated tothe central metal includes a triazole skeleton including nitrogen bondedto the central metal, energy can be efficiently absorbed, andphosphorescence having an emission spectrum with a peak at around 500 nmcan be obtained with high emission quantum efficiency. In the four typesof ligands coordinated to the central metal, an indolo[3,2-b]carbazoleskeleton whose 6-position is bonded to the central metal or apyrido[2,3-b:6,5-b′]diindole skeleton whose 6-position is bonded to thecentral metal; a benzene skeleton whose carbon is bonded to the centralmetal; and a pyridine skeleton whose nitrogen is bonded to the centralmetal or a benzene skeleton whose carbon is bonded to the central metalare bonded to one another through nitrogen of an indolo[3,2-b]carbazoleskeleton whose 6-position is bonded to the central metal or apyrido[2,3-b:6,5-b′]diindole skeleton whose 6-position is bonded to thecentral metal, and therefore, the above-described organometallic complexwhich is one embodiment of the present invention has a rigid structure.Thus, the molecular structure is stabilized and less likely to bedistorted, and therefore, the heat resistance can be improved, and theoscillator strength of electron transition between the lowestvibrational levels (0-0 transition) in which transition energy ofabsorption is equal to that of light emission is increased because adifference between the bond length of atoms in a ground state and thebond length of atoms in an excited state is extremely small, so that anemission spectrum can be further narrowed, and phosphorescence with highcolor purity can be obtained.

Next, specific structural formulae of the above-described organometalliccomplexes, each of which is one embodiment of the present invention, areshown below. Note that the present invention is not limited to theseexamples.

Note that organometallic complexes represented by the structuralformulae (100) to (109), (200) to (205), and (301) to (305) are novelsubstances capable of emitting phosphorescence. Note that there can begeometrical isomers and stereoisomers of these substances depending onthe type of the ligand. Each of the organometallic complexes which areembodiments of the present invention includes all of these isomers.

Next, an example of a method of synthesizing the organometallic complexwhich is one embodiment of the present invention and represented by theabove general formula (G1) is described.

<<Synthesis Method of a Derivative Represented by the General Formula(G0)>>

A derivative represented by the general formula (G0) below can besynthesized by a simple synthesis scheme (A) as follows. In thesynthesis scheme (A), X represents a halogen.

Note that in the general formula (G0), each of R¹ to R¹⁶ independentlyrepresents any of hydrogen, an alkyl group having 1 to 6 carbon atoms,and a substituted or unsubstituted aryl group having 6 to 13 carbonatoms, and one of Q¹ and Q² represents nitrogen, and the other thereofrepresents carbon. Furthermore, a ring A represents a triazole ring.

For example, as shown in the scheme (A) below, the derivativerepresented by the general formula (G0) can be obtained by coupling ofan indolo[3,2-b]carbazole skeleton or a pyrido[2,3-b:6,5-b′]diindoleskeleton whose 6-position is bonded to the central metal (A1), ahalogenated pyridine compound or a halogenated benzene compound (A2),and a halogenated triazole compound (A3).

A wide variety of the compounds (A1) to (A3) can be obtained orsynthesized, and thus a great variety of the derivatives represented bythe general formula (G0) can be synthesized. Thus, a feature of theorganometallic complex which is one embodiment of the present inventionis the abundance of ligand variations.

Next, as shown in a synthesis scheme (B) below, heating is performed inan inert gas atmosphere using the derivative represented by the generalformula (G0); palladium including halogen or a metal compound ofplatinum including halogen (e.g., palladium chloride or potassiumtetrachloroplatinate); and acetic acid or a solvent including aceticacid. Thus, the organometallic complex which is one embodiment of thepresent invention and represented by the general formula (G1) can beobtained.

In the synthesis scheme (B), M represents Pt or Pd. Each of R¹ to R¹⁶independently represents any of hydrogen, an alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted aryl group having 6 to13 carbon atoms. One of Q¹ and Q² represents nitrogen, and the otherthereof represents carbon. Furthermore, a ring A represents a triazolering.

The above is the description of the example of a method of synthesizingan organometallic complex which is one embodiment of the presentinvention; however, the present invention is not limited thereto and anyother synthesis method may be employed.

The above-described organometallic complex which is one embodiment ofthe present invention can emit phosphorescence and thus can be used as alight-emitting material or a light-emitting substance of alight-emitting element.

With the use of the organometallic complex which is one embodiment ofthe present invention, a light-emitting element, a light-emittingdevice, an electronic device, or a lighting device with high emissionefficiency can be obtained. Alternatively, it is possible to obtain alight-emitting element, a light-emitting device, an electronic device,or a lighting device with low power consumption.

In this embodiment, one embodiment of the present invention isdescribed. Other embodiments of the present invention are described inother embodiments. Note that one embodiment of the present invention isnot limited thereto. That is, since various embodiments of the presentinvention are disclosed in this embodiment and the other embodiments,one embodiment of the present invention is not limited to a specificembodiment. The example in which one embodiment of the present inventionis applied to a light-emitting element is described; however, oneembodiment of the present invention is not limited thereto. Depending oncircumstances or conditions, one embodiment of the present invention maybe applied to objects other than a light-emitting element.

The structure described in this embodiment can be combined asappropriate with any of the structures described in other embodiments.

(Embodiment 2)

In this embodiment, a light-emitting element which is one embodiment ofthe present invention will be described with reference to FIGS. 1A and1B.

In the light-emitting element described in this embodiment, an EL layer102 including a light-emitting layer 113 is interposed between a pair ofelectrodes (a first electrode (anode) 101 and a second electrode(cathode) 103), and the EL layer 102 includes a hole-injection layer111, a hole-transport layer 112, an electron-transport layer 114, anelectron-injection layer 115, and the like in addition to thelight-emitting layer 113.

When a voltage is applied to the light-emitting element, holes injectedfrom the first electrode 101 side and electrons injected from the secondelectrode 103 side recombine in the light-emitting layer 113; withenergy generated by the recombination, a light-emitting substance suchas the organometallic complex that is contained in the light-emittinglayer 113 emits light.

The hole-injection layer 111 in the EL layer 102 can inject holes intothe hole-transport layer 112 or the light-emitting layer 113 and can beformed of, for example, a substance having a high hole-transportproperty and a substance having an acceptor property, in which caseelectrons are extracted from the substance having a high hole-transportproperty by the substance having an acceptor property to generate holes.Thus, holes are injected from the hole-injection layer 111 into thelight-emitting layer 113 through the hole-transport layer 112. For thehole-injection layer ill, a substance having a high hole-injectionproperty can also be used. For example, molybdenum oxide, vanadiumoxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like canbe used. Alternatively, the hole-injection layer 111 can be formed usinga phthalocyanine-based compound such as phthalocyanine (abbreviation:H₂Pc) and copper phthalocyanine (CuPc), an aromatic amine compound suchas 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation: DPAB) andN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD), or a high molecular compound such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS).

A preferred specific example in which the light-emitting elementdescribed in this embodiment is fabricated is described below.

For the first electrode (anode) 101 and the second electrode (cathode)103, a metal, an alloy, an electrically conductive compound, a mixturethereof, and the like can be used. Specific examples are indiumoxide-tin oxide (indium tin oxide), indium oxide-tin oxide containingsilicon or silicon oxide, indium oxide-zinc oxide (indium zinc oxide),indium oxide containing tungsten oxide and zinc oxide, gold (Au),platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum(Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and titanium(Ti). In addition, an element belonging to Group 1 or Group 2 of theperiodic table, for example, an alkali metal such as lithium (Li) orcesium (Cs), an alkaline earth metal such as calcium (Ca) or strontium(Sr), magnesium (Mg), an alloy containing such an element (MgAg orAlLi), a rare earth metal such as europium (Eu) or ytterbium (Yb), analloy containing such an element, graphene, and the like can be used.The first electrode (anode) 101 and the second electrode (cathode) 103can be formed by, for example, a sputtering method or an evaporationmethod (including a vacuum evaporation method).

As the substance having a high hole-transport property which is used forthe hole-injection layer 111 and the hole-transport layer 112, any of avariety of organic compounds such as aromatic amine compounds, carbazolederivatives, aromatic hydrocarbons, and high molecular compounds (e.g.,oligomers, dendrimers, or polymers) can be used. Note that the organiccompound used for the composite material is preferably an organiccompound having a high hole-transport property. Specifically, asubstance having a hole mobility of 1×10⁻⁶ cm²/Vs or more is preferablyused. The layer formed using the substance having a high hole-transportproperty is not limited to a single layer and may be formed by stackingtwo or more layers. Organic compounds that can be used as the substancehaving a hole-transport property are specifically given below.

Examples of the aromatic amine compounds areN,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation:DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation: DPAB), DNTPD,1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB or α-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), and the like.

Specific examples of carbazole derivatives are3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), and the like. Other examples are4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB),9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA),1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, and thelike.

Examples of aromatic hydrocarbons are2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA),2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA),9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene(abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA),2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene,9,10-bis[2-(1-naphthyl)phenyl]anthracene,2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene,2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl,10,10′-diphenyl-9,9′-bianthryl,10,10′-bis(2-phenylphenyl)-9,9′-bianthryl,10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene,tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, andthe like. Besides, pentacene, coronene, or the like can also be used.The aromatic hydrocarbon which has a hole mobility of 1×10⁻⁶ cm²/Vs ormore and which has 14 to 42 carbon atoms is particularly preferable. Thearomatic hydrocarbons may have a vinyl skeleton. Examples of thearomatic hydrocarbon having a vinyl group are4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can also be used.

Examples of the substance having an acceptor property which is used forthe hole-injection layer 111 and the hole-transport layer 112 arecompounds having an electron-withdrawing group (a halogen group or acyano group) such as7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN). Inparticular, a compound in which electron-withdrawing groups are bondedto a condensed aromatic ring having a plurality of hetero atoms, likeHAT-CN, is thermally stable and preferable. Oxides of metals belongingto Groups 4 to 8 of the periodic table can be given. Specifically,vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide arepreferable because of their high electron-accepting properties. Amongthese, molybdenum oxide is especially preferable since it is stable inthe air and its hygroscopic property is low and is easily treated.

The light-emitting layer 113 contains a light-emitting substance, whichmay be a fluorescent substance or a phosphorescent substance. In thelight-emitting element which is one embodiment of the present invention,the organometallic complex described in Embodiment 1 is preferably usedas the light-emitting substance in the light-emitting layer 113. Thelight-emitting layer 113 preferably contains, as a host material, asubstance having higher triplet excitation energy than thisorganometallic complex (guest material). Alternatively, thelight-emitting layer 113 may contain, in addition to the light-emittingsubstance, two kinds of organic compounds that can form an excitedcomplex (also called an exciplex) at the time of recombination ofcarriers (electrons and holes) in the light-emitting layer 113 (the twokinds of organic compounds may be any of host materials as describedabove). In order to form an exciplex efficiently, it is particularlypreferable to combine a compound which easily accepts electrons (amaterial having an electron-transport property) and a compound whicheasily accepts holes (a material having a hole-transport property). Inthe case where the combination of a material having anelectron-transport property and a material having a hole-transportproperty which form an exciplex is used as a host material as describedabove, the carrier balance between holes and electrons in thelight-emitting layer can be easily optimized by adjustment of themixture ratio of the material having an electron-transport property andthe material having a hole-transport property. The optimization of thecarrier balance between holes and electrons in the light-emitting layercan prevent a region in which electrons and holes are recombined fromexisting on one side in the light-emitting layer. By preventing theregion in which electrons and holes are recombined from existing to oneside, the reliability of the light-emitting element can be improved.

As the compound that is preferably used to form the above exciplex andeasily accepts electrons (material having an electron-transportproperty), a n-electron deficient heteroaromatic compound such as anitrogen-containing heteroaromatic compound, a metal complex, or thelike can be used. Specific examples include metal complexes such asbis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds having polyazole skeletons, such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), and2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); heterocyclic compounds having diazineskeletons, such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[a]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 6mDBTPDBq-II),4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation:4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine(abbreviation: 4,6mDBTP2Pm-II), and 4,6-bis[3-(9H-carbazol-9-yl)-phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm);a heterocyclic compound having a triazine skeleton such as2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(abbreviation: PCCzPTzn); and heterocyclic compounds having pyridineskeletons, such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine(abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene(abbreviation: TmPyPB). Among the above materials, the heterocycliccompounds having diazine skeletons, those having triazine skeletons, andthose having pyridine skeletons are highly reliable and preferred. Inparticular, the heterocyclic compounds having diazine (pyrimidine orpyrazine) skeletons and those having triazine skeletons have a highelectron-transport property and contribute to a decrease in drivevoltage.

As the compound that is preferably used to form the above exciplex andeasily accepts holes (the material having a hole-transport property), aπ-electron rich heteroaromatic compound (e.g., a carbazole derivative oran indole derivative), an aromatic amine compound, or the like can befavorably used. Specific examples include compounds having aromaticamine skeletons, such as2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N′-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F), NPB,N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB), BSPB, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N′-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL), PCzPCA1,3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2), DNTPD,3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2), PCzPCA2,4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF),N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF),N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine(abbreviation: PCBiF), andN-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine(abbreviation: PCBBiF); compounds having carbazole skeletons, such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), CBP,3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP);compounds having thiophene skeletons, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and compounds having furan skeletons, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II)and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II). Among the above materials, the compoundshaving aromatic amine skeletons and the compounds having carbazoleskeletons are preferred because these compounds are highly reliable andhave a high hole-transport property and contribute to a reduction indrive voltage.

Note that in the case where the light-emitting layer 113 contains theabove-described organometallic complex (guest material) and the hostmaterial, phosphorescence with high emission efficiency can be obtainedfrom the light-emitting layer 113.

In the light-emitting element, the light-emitting layer 113 does notnecessarily have the single-layer structure shown in FIG. 1A and mayhave a stacked-layer structure including two or more layers as shown inFIG. 1B. In that case, each layer in the stacked-layer structure emitslight. For example, fluorescence is obtained from a first light-emittinglayer 113(a 1), and phosphorescence is obtained from a secondlight-emitting layer 113(a 2) stacked over the first light-emittinglayer. Note that the stacking order may be reversed. It is preferablethat light emission due to energy transfer from an exciplex to a dopantbe obtained from the layer that emits phosphorescence. The emissioncolor of one layer and that of the other layer may be the same ordifferent. In the case where the emission colors are different, astructure in which, for example, blue light from one layer and orange oryellow light or the like from the other layer can be obtained can beformed. Each layer may contain various kinds of dopants.

Note that in the case where the light-emitting layer 113 has astacked-layer structure, for example, the organometallic complexdescribed in Embodiment 1, a light-emitting substance converting singletexcitation energy into light emission, and a light-emitting substanceconverting triplet excitation energy into light emission can be usedalone or in combination. In that case, the following substances can beused.

As an example of the light-emitting substance converting singletexcitation energy into light emission, a substance which emitsfluorescence (a fluorescent compound) can be given.

Examples of the substance emitting fluorescence areN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl1,4-phenylenediamine (abbreviation: 2DPAPPA),N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCM1),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM),2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: BisDCJTM), and the like.

Examples of the light-emitting substance converting triplet excitationenergy into light emission are a substance which emits phosphorescence(a phosphorescent compound) and a thermally activated delayedfluorescent (TADF) material which emits thermally activated delayedfluorescence. Note that “delayed fluorescence” exhibited by the TADFmaterial refers to light emission having the same spectrum as normalfluorescence and an extremely long lifetime. The lifetime is 1×10⁻⁶seconds or longer, preferably 1×10⁻³ seconds or longer.

Examples of the substance emitting phosphorescence arebis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)],bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIracac),tris(2-phenylpyridinato)iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato)iridium(III) acetylacetonate (abbreviation:[Ir(ppy)₂(acac)]), tris(acetylacetonato)(monophenanthroline)terbium(III)(abbreviation: [Tb(acac)₃(Phen)]), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: [Ir(bzq)₂(acac)]),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(bt)₂(acac)]),bis[2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C^(3′)]iridium(III)acetylacetonate (abbreviation: [Ir(btp)₂(acac)]),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(piq)₂(acac)]),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]),(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]),(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]),(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)],(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP),tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]),tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]), and the like.

Examples of the TADF material are fullerene, a derivative thereof, anacridine derivative such as proflavine, eosin, and the like. Otherexamples are a metal-containing porphyrin, such as a porphyrincontaining magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum(Pt), indium (In), or palladium (Pd). Examples of the metal-containingporphyrin are a protoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), anoctaethylporphyrin-platinum chloride complex (PtCl₂OEP), and the like.Alternatively, a heterocyclic compound including a π-electron richheteroaromatic ring and a π-electron deficient heteroaromatic ring canbe used, such as2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(PIC-TRZ). Note that a material in which the n-electron richheteroaromatic ring is directly bonded to the π-electron deficientheteroaromatic ring is particularly preferably used because both thedonor property of the π-electron rich heteroaromatic ring and theacceptor property of the n-electron deficient heteroaromatic ring areincreased and the energy difference between the Si level and the T1level becomes small.

The electron-transport layer 114 is a layer containing a substancehaving a high electron-transport property (also referred to as anelectron-transport compound). For the electron-transport layer 114, ametal complex such as tris(8-quinolinolato)aluminum (abbreviation:Alq₃), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),BeBq₂, BAlq, bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation:Zn(BOX)₂, or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂) can be used. Alternatively, a heteroaromatic compound such asPBD, 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7), TAZ,3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can alsobe used. A high molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can also be used. The substances listed here aremainly ones that have an electron mobility of 1×10⁻⁶ cm²/Vs or higher.Note that any substance other than the substances listed here may beused for the electron-transport layer 114 as long as theelectron-transport property is higher than the hole-transport property.

The electron-transport layer 114 is not limited to a single layer, butmay be a stack of two or more layers each containing any of thesubstances listed above.

The electron-injection layer 115 is a layer containing a substancehaving a high electron-injection property. For the electron-injectionlayer 115, an alkali metal, an alkaline earth metal, or a compoundthereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calciumfluoride (CaF₂), or lithium oxide (LiO_(x)) can be used. A rare earthmetal compound like erbium fluoride (ErF₃) can also be used. Anelectride may also be used for the electron-injection layer 115.Examples of the electride include a substance in which electrons areadded at high concentration to calcium oxide-aluminum oxide. Any of thesubstances for forming the electron-transport layer 114, which are givenabove, can be used.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the electron-injection layer 115.Such a composite material is excellent in an electron-injection propertyand an electron-transport property because electrons are generated inthe organic compound by the electron donor. In this case, the organiccompound is preferably a material that is excellent in transporting thegenerated electrons. Specifically, for example, the substances forforming the electron-transport layer 114 (e.g., a metal complex or aheteroaromatic compound), which are given above, can be used. As theelectron donor, a substance showing an electron-donating property withrespect to the organic compound may be used. Specifically, an alkalimetal, an alkaline earth metal, and a rare earth metal are preferable,and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the likeare given. In addition, an alkali metal oxide or an alkaline earth metaloxide is preferable, and lithium oxide, calcium oxide, barium oxide, andthe like are given. A Lewis base such as magnesium oxide can also beused. An organic compound such as tetrathiafulvalene (abbreviation: TTF)can also be used.

Note that each of the hole-injection layer 111, the hole-transport layer112, the light-emitting layer 113, the electron-transport layer 114, andthe electron-injection layer 115 can be formed by any one or anycombination of the following methods: an evaporation method (including avacuum evaporation method), a printing method (such as relief printing,intaglio printing, gravure printing, planography printing, and stencilprinting), an ink-jet method, a coating method, and the like. Besidesthe above-mentioned materials, an inorganic compound such as a quantumdot or a high molecular compound (e.g., an oligomer, a dendrimer, or apolymer) may be used for the hole-injection layer 111, thehole-transport layer 112, the light-emitting layer 113, theelectron-transport layer 114, and the electron-injection layer 115,which are described above.

In the above-described light-emitting element, current flows due to apotential difference applied between the first electrode 101 and thesecond electrode 103 and holes and electrons recombine in the EL layer102, whereby light is emitted. Then, the emitted light is extractedoutside through one or both of the first electrode 101 and the secondelectrode 103. Thus, one or both of the first electrode 101 and thesecond electrode 103 are electrodes having light-transmittingproperties.

The above-described light-emitting element can emit phosphorescenceoriginating from the organometallic complex and thus can have higherefficiency than a light-emitting element using only a fluorescentcompound.

The structure described in this embodiment can be used in appropriatecombination with the structure described in any of other embodiments.

(Embodiment 3)

In this embodiment, a light-emitting element (hereinafter referred to asa tandem light-emitting element) which is one embodiment of the presentinvention and includes a plurality of EL layers is described.

A light-emitting element described in this embodiment is a tandemlight-emitting element including, between a pair of electrodes (a firstelectrode 201 and a second electrode 204), a plurality of EL layers (afirst EL layer 202(1) and a second EL layer 202(2)) and acharge-generation layer 205 provided therebetween, as illustrated inFIG. 2A.

In this embodiment, the first electrode 201 functions as an anode, andthe second electrode 204 functions as a cathode. Note that the firstelectrode 201 and the second electrode 204 can have structures similarto those described in Embodiment 2. In addition, either or both of theEL layers (the first EL layer 202(1) and the second EL layer 202(2)) mayhave structures similar to those described in Embodiment 2. In otherwords, the structures of the first EL layer 202(1) and the second ELlayer 202(2) may be the same as or different from each other. When thestructures are the same, Embodiment 2 can be referred to.

The charge-generation layer 205 provided between the plurality of ELlayers (the first EL layer 202(1) and the second EL layer 202(2)) has afunction of injecting electrons into one of the EL layers and injectingholes into the other of the EL layers when a voltage is applied betweenthe first electrode 201 and the second electrode 204. In thisembodiment, when a voltage is applied such that the potential of thefirst electrode 201 is higher than that of the second electrode 204, thecharge-generation layer 205 injects electrons into the first EL layer202(1) and injects holes into the second EL layer 202(2).

Note that in terms of light extraction efficiency, the charge-generationlayer 205 preferably has a property of transmitting visible light(specifically, the charge-generation layer 205 has a visible lighttransmittance of 40% or more). The charge-generation layer 205 functionseven when it has lower conductivity than the first electrode 201 or thesecond electrode 204.

The charge-generation layer 205 may have either a structure in which anelectron acceptor (acceptor) is added to an organic compound having ahigh hole-transport property or a structure in which an electron donor(donor) is added to an organic compound having a high electron-transportproperty. Alternatively, both of these structures may be stacked.

In the case of the structure in which an electron acceptor is added toan organic compound having a high hole-transport property, as theorganic compound having a high hole-transport property, the substanceshaving a high hole-transport property which are given in Embodiment 2 asthe substances used for the hole-injection layer 111 and thehole-transport layer 112 can be used. For example, an aromatic aminecompound such as NPB, TPD, TDATA, MTDATA, or BSPB, or the like can beused. The substances listed here are mainly ones that have a holemobility of 1×10⁻⁶ cm²/Vs or higher. Note that any organic compoundother than the compounds listed here may be used as long as thehole-transport property is higher than the electron-transport property.

As the electron acceptor,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like can be given. Oxides of metalsbelonging to Groups 4 to 8 of the periodic table can also be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, and rheniumoxide are preferable because of their high electron-acceptingproperties. Among these, molybdenum oxide is especially preferable sinceit is stable in the air and its hygroscopic property is low and iseasily treated.

In the case of the structure in which an electron donor is added to anorganic compound having a high electron-transport property, as theorganic compound having a high electron-transport property, thesubstances having a high electron-transport property which are given inEmbodiment 2 as the substances used for the electron-transport layer 114can be used. For example, a metal complex having a quinoline skeleton ora benzoquinoline skeleton, such as Alq, Almq₃, BeBq₂, or BAlq, or thelike can be used. Alternatively, a metal complex having an oxazole-basedligand or a thiazole-based ligand, such as Zn(BOX)₂ or Zn(BTZ)₂ can beused. Alternatively, in addition to such a metal complex, PBD, OXD-7,TAZ, Bphen, BCP, or the like can be used. The substances listed here aremainly ones that have an electron mobility of 1×10⁻⁶ cm²/Vs or higher.Note that any organic compound other than the compounds listed here maybe used as long as the electron-transport property is higher than thehole-transport property.

As the electron donor, it is possible to use an alkali metal, analkaline earth metal, a rare earth metal, metals belonging to Groups 2and 13 of the periodic table, or an oxide or carbonate thereof.Specifically, lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca),ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, or thelike is preferably used. Alternatively, an organic compound such astetrathianaphthacene may be used as the electron donor.

Note that foci ling the charge-generation layer 205 by using any of theabove materials can suppress a drive voltage increase caused by thestack of the EL layers. The charge-generation layer 205 can be formed byany one or any combination of the following methods: an evaporationmethod (including a vacuum evaporation method), a printing method (suchas relief printing, intaglio printing, gravure printing, planographyprinting, and stencil printing), an ink-jet method, a coating method,and the like.

Although the light-emitting element including two EL layers is describedin this embodiment, the present invention can be similarly applied to alight-emitting element in which n EL layers (202(1) to 202(n)) (n isthree or more) are stacked as illustrated in FIG. 2B. In the case wherea plurality of EL layers are included between a pair of electrodes as inthe light-emitting element according to this embodiment, by providingcharge-generation layers (205(1) to 205(n−1)) between the EL layers,light emission in a high luminance region can be obtained with currentdensity kept low. Since the current density can be kept low, the elementcan have a long lifetime.

When the EL layers have different emission colors, a desired emissioncolor can be obtained from the whole light-emitting element. Forexample, in a light-emitting element having two EL layers, when anemission color of the first EL layer and an emission color of the secondEL layer are complementary colors, the light-emitting element can emitwhite light as a whole. Note that “complementary colors” refer to colorsthat can produce an achromatic color when mixed. In other words, mixinglight of complementary colors allows white light emission to beobtained. Specifically, a combination in which blue light emission isobtained from the first EL layer and yellow or orange light emission isobtained from the second EL layer is given as an example. In that case,it is not necessary that both of blue light emission and yellow (ororange) light emission are fluorescence, and the both are notnecessarily phosphorescence. For example, a combination in which bluelight emission is fluorescence and yellow (or orange) light emission isphosphorescence or a combination in which blue light emission isphosphorescence and yellow (or orange) light emission is fluorescencemay be employed.

The same can be applied to a light-emitting element having three ELlayers. For example, the light-emitting element as a whole can providewhite light emission when the emission color of the first EL layer isred, the emission color of the second EL layer is green, and theemission color of the third EL layer is blue.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in other embodiments.

(Embodiment 4)

In this embodiment, a light-emitting device which is one embodiment ofthe present invention is described.

The light-emitting device may be either a passive matrix light-emittingdevice or an active matrix light-emitting device. Any of thelight-emitting elements described in other embodiments can be used forthe light-emitting device described in this embodiment.

In this embodiment, first, an active matrix light-emitting device isdescribed with reference to FIGS. 3A to 3C.

Note that FIG. 3A is a top view illustrating a light-emitting device andFIG. 3B is a cross-sectional view taken along the chain line A-A′ inFIG. 3A. The active matrix light-emitting device includes a pixelportion 302 provided over an element substrate 301, a driver circuitportion (a source line driver circuit) 303, and driver circuit portions(gate line driver circuits) 304 a and 304 b. The pixel portion 302, andthe driver circuit portions 304 a and 304 b are sealed between theelement substrate 301 and a sealing substrate 306 with a sealant 305.

In addition, over the element substrate 301, a lead wiring 307 forconnecting an external input terminal, through which a signal (e.g., avideo signal, a clock signal, a start signal, or a reset signal) or anpotential from the outside is transmitted to the driver circuit portion303 and the driver circuit portions 304 a and 304 b, is provided. Here,an example is described in which a flexible printed circuit (FPC) 308 isprovided as the external input terminal. Although only the FPC isillustrated here, the FPC may be provided with a printed wiring board(PWB). The light-emitting device in this specification includes, in itscategory, not only the light-emitting device itself but also thelight-emitting device provided with the FPC or the PWB.

Next, a cross-sectional structure is described with reference to FIG.3B. The driver circuit portions and the pixel portion are formed overthe element substrate 301; the driver circuit portion 303 that is thesource line driver circuit and the pixel portion 302 are illustratedhere.

The driver circuit portion 303 is an example in which an FET 309 and anFET 310 are combined. Note that the driver circuit portion 303 may beformed with a circuit including transistors having the same conductivitytype (either n-channel transistors or p-channel transistors) or a CMOScircuit including an n-channel transistor and a p-channel transistor.Although this embodiment shows a driver integrated type in which thedriver circuit is formed over the substrate, the driver circuit is notnecessarily formed over the substrate, and may be formed outside thesubstrate.

The pixel portion 302 includes a switching FET (not shown) and a currentcontrol FET 312, and a wiring of the current control FET 312 (a sourceelectrode or a drain electrode) is electrically connected to firstelectrodes (anodes) (313 a and 313 b) of light-emitting elements 317 aand 317 b. Although the pixel portion 302 includes two FETs (theswitching FET and the current control FET 312) in this embodiment, oneembodiment of the present invention is not limited thereto. The pixelportion 302 may include, for example, three or more FETs and a capacitorin combination.

As the FETs 309, 310, and 312, for example, a staggered transistor or aninverted staggered transistor can be used. Examples of a semiconductormaterial that can be used for the FETs 309, 310, and 312 are a Group 13semiconductor, a Group 14 semiconductor (e.g., silicon), a compoundsemiconductor, an oxide semiconductor, and an organic semiconductor. Inaddition, there is no particular limitation on the crystallinity of thesemiconductor material, and an amorphous semiconductor or a crystallinesemiconductor can be used. In particular, an oxide semiconductor ispreferably used for the FETs 309, 310, 311, and 312. Examples of theoxide semiconductor are In—Ga oxides, In-M-Zn oxides (M is Al, Ga, Y,Zr, La, Ce, Hf, or Nd), and the like. For example, an oxidesemiconductor that has an energy gap of 2 eV or more, preferably 2.5 eVor more, further preferably 3 eV or more is used, so that the off-statecurrent of the transistors can be reduced.

In addition, conductive films (320 a and 320 b) for optical adjustmentare stacked over the first electrodes 313 a and 313 b. For example, asillustrated in FIG. 3B, in the case where the wavelengths of lightextracted from the light-emitting elements 317 a and 317 b are differentfrom each other, the thicknesses of the conductive films 320 a and 320 bare different from each other. In addition, an insulator 314 is formedto cover end portions of the first electrodes (313 a and 313 b). In thisembodiment, the insulator 314 is formed using a positive photosensitiveacrylic resin. The first electrodes (313 a and 313 b) are used as anodesin this embodiment.

The insulator 314 preferably has a curved surface with curvature at anupper end portion or a lower end portion thereof. This enables thecoverage with a film to be formed over the insulator 314 to befavorable. The insulator 314 can be formed using, for example, either anegative photosensitive resin or a positive photosensitive resin. Thematerial for the insulator 314 is not limited to an organic compound andan inorganic compound such as silicon oxide, silicon oxynitride, orsilicon nitride can also be used.

An EL layer 315 and a second electrode 316 are stacked over the firstelectrodes (313 a and 313 b). In the EL layer 315, at least alight-emitting layer is provided. In the light-emitting elements (317 aand 317 b) including the first electrodes (313 a and 313 b), the ELlayer 315, and the second electrode 316, an end portion of the EL layer315 is covered with the second electrode 316. The structure of the ELlayer 315 may be the same as or different from the single-layerstructure and the stacked layer structure described in Embodiments 2 and3. Furthermore, the structure may differ between the light-emittingelements.

For the first electrode 313, the EL layer 315, and the second electrode316, any of the materials given in Embodiment 2 can be used. The firstelectrodes (313 a and 313 b) of the light-emitting elements (317 a and317 b) are electrically connected to a lead wiring 307 in a region 321,so that an external signal is input through the FPC 308. The secondelectrode 316 in the light-emitting elements (317 a and 317 b) iselectrically connected to a lead wiring 323 in a region 322, so that anexternal signal is input through the FPC 308 that is not illustrated inthe figure.

Although the cross-sectional view in FIG. 3B illustrates only the twolight-emitting elements 317, a plurality of light-emitting elements arearranged in a matrix in the pixel portion 302. Specifically, in thepixel portion 302, light-emitting elements that emit light of two kindsof colors (e.g., B and Y), light-emitting elements that emit light ofthree kinds of colors (e.g., R, G, and B), light-emitting elements thatemit light of four kinds of colors (e.g. (R, G, B, and Y) or (R, G, B,and W)), or the like are formed so that a light-emitting device capableof full color display can be obtained. In such cases, full color displaymay be achieved as follows: materials different according to theemission colors or the like of the light-emitting elements are used toform light-emitting layers (so-called separate coloring formation);alternatively, the plurality of light-emitting elements share onelight-emitting layer formed using the same material and further includecolor filters. Thus, the light-emitting elements that emit light of aplurality of kinds of colors are used in combination, so that effectssuch as an improvement in color purity and a reduction in powerconsumption can be achieved. Furthermore, the light-emitting device mayhave improved emission efficiency and reduced power consumption bycombination with quantum dots.

The sealing substrate 306 is attached to the element substrate 301 withthe sealant 305, whereby the light-emitting elements 317 are provided ina space 318 surrounded by the element substrate 301, the sealingsubstrate 306, and the sealant 305.

The sealing substrate 306 is provided with coloring layers (colorfilters) 324, and a black layer (black matrix) 325 is provided betweenadjacent coloring layers. Note that one or both of the adjacent coloringlayers (color filters) 324 may be provided so as to partly overlap withthe black layer (black matrix) 325. Light emission obtained from thelight-emitting elements 317 a and 317 b is extracted through thecoloring layers (color filters) 324.

Note that the space 318 may be filled with an inert gas (such asnitrogen or argon) or the sealant 305. In the case where the sealant isapplied for attachment of the substrates, one or more of UV treatment,heat treatment, and the like are preferably performed.

An epoxy-based resin or glass frit is preferably used for the sealant305. The material preferably allows as little moisture and oxygen aspossible to penetrate. As the sealing substrate 306, a glass substrate,a quartz substrate, or a plastic substrate formed of fiber-reinforcedplastic (FRP), poly(vinyl fluoride) (PVF), polyester, an acrylic resin,or the like can be used. In the case where glass frit is used as thesealant, the element substrate 301 and the sealing substrate 306 arepreferably glass substrates for high adhesion.

Structures of the FETs electrically connected to the light-emittingelements may be different from those in FIG. 3B in the position of agate electrode; that is, the structures may be the same as those of aFET 326, a FET 327, and a FET 328, as illustrated in FIG. 3C. Thecoloring layer (color filter) 324 with which the sealing substrate 306is provided may be provided as illustrated in FIG. 3C such that, at aposition where the coloring layer (color filter) 324 overlaps with theblack layer (black matrix) 325, the coloring layer (color filter) 324further overlaps with an adjacent coloring layer (color filter) 324.

As described above, the active matrix light-emitting device can beobtained.

The light-emitting device which is one embodiment of the presentinvention may be of the passive matrix type, instead of the activematrix type described above.

FIGS. 4A and 4B illustrate a passive-matrix light-emitting device. FIG.4A is a top view of the passive-matrix light-emitting device, and FIG.4B is a cross-sectional view thereof.

As illustrated in FIG. 4A, light-emitting elements 405 including a firstelectrode 402, EL layers (403 a, 403 b, and 403 c), and secondelectrodes 404 are formed over a substrate 401. Note that the firstelectrode 402 has an island-like shape, and a plurality of the firstelectrodes 402 are formed in one direction (the lateral direction inFIG. 4A) to form a striped pattern. An insulating film 405 is formedover part of the first electrode 402. A partition 406 formed using aninsulating material is provided over the insulating film 405. Thesidewalls of the partition 406 slope so that the distance between onesidewall and the other sidewall gradually decreases toward the surfaceof the substrate as illustrated in FIG. 4B.

Since the insulating film 405 includes openings over the part of thefirst electrode 402, the EL layers (403 a, 403 b, and 403 c) and secondelectrodes 404 which are divided as desired can be formed over the firstelectrode 402. In the example in FIGS. 4A and 4B, a mask such as a metalmask and the partition 406 over the insulating film 405 are employed toform the EL layers (403 a, 403 b, and 403 c) and the second electrodes404. In this example, the EL layer 403 a, the EL layer 403 b, and the ELlayer 403 c emit light of different colors (e.g., red, green, blue,yellow, orange, and white).

After the formation of the EL layers (403 a, 403 b, and 403 c), thesecond electrodes 404 are formed. Thus, the second electrode 404 isformed over the EL layers (403 a, 403 b, and 403 c) without contact withthe first electrode 402.

Note that sealing can be performed by a method similar to that used forthe active matrix light-emitting device, and description thereof is notmade.

As described above, the passive matrix light-emitting device can beobtained.

Note that in this specification and the like, a transistor or alight-emitting element can be formed using any of a variety ofsubstrates, for example. The type of a substrate is not limited to acertain type. As the substrate, a semiconductor substrate (e.g., asingle crystal substrate or a silicon substrate), an SOI substrate, aglass substrate, a quartz substrate, a plastic substrate, a metalsubstrate, a stainless steel substrate, a substrate including stainlesssteel foil, a tungsten substrate, a substrate including tungsten foil, aflexible substrate, an attachment film, paper including a fibrousmaterial, a base material film, or the like can be used, for example. Asan example of a glass substrate, a barium borosilicate glass substrate,an aluminoborosilicate glass substrate, a soda lime glass substrate, orthe like can be given. Examples of the flexible substrate, theattachment film, the base material film, and the like are substrates ofplastics typified by polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyether sulfone (PES), and polytetrafluoroethylene(PTFE). Another example is a synthetic resin such as acrylic.Alternatively, polypropylene, polyester, polyvinyl fluoride, polyvinylchloride, or the like can be used. Alternatively, polyamide, polyimide,aramid, epoxy, an inorganic vapor deposition film, paper, or the likecan be used. Specifically, the use of semiconductor substrates, singlecrystal substrates, SOI substrates, or the like enables the manufactureof small-sized transistors with a small variation in characteristics,size, shape, or the like and with high current supply capability. Acircuit using such transistors achieves lower power consumption of thecircuit or higher integration of the circuit.

Alternatively, a flexible substrate may be used as the substrate, and atransistor or a light-emitting element may be provided directly on theflexible substrate. Still alternatively, a separation layer may beprovided between the substrate and the transistor or the light-emittingelement. The separation layer can be used when part or the whole of asemiconductor device formed over the separation layer is separated fromthe substrate and transferred onto another substrate. In such a case,the transistor or the light-emitting element can be transferred to asubstrate having low heat resistance or a flexible substrate. For theseparation layer, a stack including inorganic films, which are atungsten film and a silicon oxide film, or an organic resin film ofpolyimide or the like formed over a substrate can be used, for example.

In other words, a transistor or a light-emitting element may be formedusing one substrate, and then transferred to another substrate. Examplesof a substrate to which a transistor or a light-emitting element istransferred are, in addition to the above-described substrates overwhich a transistor or a light-emitting element can be formed, a papersubstrate, a cellophane substrate, an aramid film substrate, a polyimidefilm substrate, a stone substrate, a wood substrate, a cloth substrate(including a natural fiber (e.g., silk, cotton, or hemp), a syntheticfiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber(e.g., acetate, cupra, rayon, or regenerated polyester), or the like), aleather substrate, a rubber substrate, and the like. When such asubstrate is used, a transistor with excellent characteristics or atransistor with low power consumption can be formed, a device with highdurability or high heat resistance can be provided, or a reduction inweight or thickness can be achieved.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in other embodiments.

(Embodiment 5)

In this embodiment, examples of a variety of electronic devices and anautomobile manufactured using a light-emitting device which is oneembodiment of the present invention are described.

Examples of the electronic device including the light-emitting deviceare television devices (also referred to as TV or television receivers),monitors for computers and the like, cameras such as digital cameras anddigital video cameras, digital photo frames, cellular phones (alsoreferred to as portable telephone devices), portable game consoles,portable information terminals, audio playback devices, large gamemachines such as pachinko machines, and the like. Specific examples ofthe electronic devices are illustrated in FIGS. 5A to 5D, 5D′-1, and5D′-2 and FIGS. 6A to 6C.

FIG. 5A illustrates an example of a television device. In the televisiondevice 7100, a display portion 7103 is incorporated in a housing 7101.The display portion 7103 can display images and may be a touch panel (aninput/output device) including a touch sensor (an input device). Notethat the light-emitting device which is one embodiment of the presentinvention can be used for the display portion 7103. In addition, here,the housing 7101 is supported by a stand 7105.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the use of the receiver, general televisionbroadcasts can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 5B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer can be manufactured using the light-emitting device whichis one embodiment of the present invention for the display portion 7203.The display portion 7203 may be a touch panel (an input/output device)including a touch sensor (an input device).

FIG. 5C illustrates a smart watch, which includes a housing 7302, adisplay portion 7304, operation buttons 7311 and 7312, a connectionterminal 7313, a band 7321, a clasp 7322, and the like.

The display portion 7304 mounted in the housing 7302 serving as a bezelincludes a non-rectangular display region. The display portion 7304 candisplay an icon 7305 indicating time, another icon 7306, and the like.The display portion 7304 may be a touch panel (an input/output device)including a touch sensor (an input device).

The smart watch illustrated in FIG. 5C can have a variety of functions,such as a function of displaying a variety of information (e.g., a stillimage, a moving image, and a text image) on a display portion, a touchpanel function, a function of displaying a calendar, date, time, and thelike, a function of controlling processing with a variety of software(programs), a wireless communication function, a function of beingconnected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading program or data stored in a recording medium and displayingthe program or data on a display portion.

The housing 7302 can include a speaker, a sensor (a sensor having afunction of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), amicrophone, and the like. Note that the smart watch can be manufacturedusing the light-emitting device for the display portion 7304.

FIGS. 5D, 5D′-1, and 5D′-2 illustrate an example of a cellular phone(e.g., smartphone). A cellular phone 7400 includes a housing 7401provided with a display portion 7402, a microphone 7406, a speaker 7405,a camera 7407, an external connection portion 7404, an operation button7403, and the like. In the case where a light-emitting device ismanufactured by forming a light-emitting element of one embodiment ofthe present invention over a flexible substrate, the light-emittingelement can be used for the display portion 7402 having a curved surfaceas illustrated in FIG. 5D.

When the display portion 7402 of the cellular phone 7400 illustrated inFIG. 5D is touched with a finger or the like, data can be input to thecellular phone 7400. In addition, operations such as making a call andcomposing e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as characters. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are combined.

For example, in the case of making a call or creating e-mail, acharacter input mode mainly for inputting characters is selected for thedisplay portion 7402 so that characters displayed on the screen can beinput. In this case, it is preferable to display a keyboard or numberbuttons on almost the entire screen of the display portion 7402.

When a detection device such as a gyroscope or an acceleration sensor isprovided inside the cellular phone 7400, display on the screen of thedisplay portion 7402 can be automatically changed by determining theorientation of the cellular phone 7400 (whether the cellular phone isplaced horizontally or vertically for a landscape mode or a portraitmode).

The screen modes are changed by touch on the display portion 7402 oroperation with the operation button 7403 of the housing 7401. The screenmodes can be switched depending on the kind of images displayed on thedisplay portion 7402. For example, when a signal of an image displayedon the display portion is a signal of moving image data, the screen modeis switched to the display mode. When the signal is a signal of textdata, the screen mode is switched to the input mode.

Moreover, in the input mode, if a signal detected by an optical sensorin the display portion 7402 is detected and the input by touch on thedisplay portion 7402 is not performed for a certain period, the screenmode may be controlled so as to be changed from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. In addition, by providing abacklight or a sensing light source that emits near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

The light-emitting device can be used for a cellular phone having astructure illustrated in FIG. 5D′-1 or FIG. 5D′-2, which is anotherstructure of the cellular phone (e.g., a smartphone).

Note that in the case of the structure illustrated in FIG. 5D′-1 or FIG.5D′-2, text data, image data, or the like can be displayed on secondscreens 7502(1) and 7502(2) of housings 7500(1) and 7500(2) as well asfirst screens 7501(1) and 7501(2). Such a structure enables a user toeasily see text data, image data, or the like displayed on the secondscreens 7502(1) and 7502(2) while the cellular phone is placed in user'sbreast pocket.

Another electronic device including a light-emitting device is afoldable portable information terminal illustrated in FIGS. 6A to 6C.FIG. 6A illustrates the portable information terminal 9310 which isopened. FIG. 6B illustrates the portable information terminal 9310 whichis being opened or being folded. FIG. 6C illustrates the portableinformation terminal 9310 that is folded. The portable informationterminal 9310 is highly portable when folded. The portable informationterminal 9310 is highly browsable when opened because of a seamlesslarge display region.

A display portion 9311 is supported by three housings 9315 joinedtogether by hinges 9313. Note that the display portion 9311 may be atouch panel (an input/output device) including a touch sensor (an inputdevice). By bending the display portion 9311 at a connection portionbetween two housings 9315 with the use of the hinges 9313, the portableinformation terminal 9310 can be reversibly changed in shape from anopened state to a folded state. A light-emitting device of oneembodiment of the present invention can be used for the display portion9311. A display region 9312 in the display portion 9311 is a displayregion that is positioned at a side surface of the portable informationterminal 9310 that is folded. On the display region 9312, informationicons, file shortcuts of frequently used applications or programs, andthe like can be displayed, and confirmation of information and start ofapplication can be smoothly performed.

FIGS. 7A and 7B illustrate an automobile including a light-emittingdevice. The light-emitting device can be incorporated in the automobile,and specifically, can be included in lights 5101 (including lights ofthe rear part of the car), a wheel 5102 of a tire, a part or whole of adoor 5103, or the like on the outer side of the automobile which isillustrated in FIG. 7A. The light-emitting device can also be includedin a display portion 5104, a steering wheel 5105, a gear lever 5106, asheet 5107, a rearview mirror 5108, or the like on the inner side of theautomobile which is illustrated in FIG. 7B, or in a part of a glasswindow.

As described above, the electronic devices and automobiles can beobtained using the light-emitting device which is one embodiment of thepresent invention. Note that the light-emitting device can be used forelectronic devices and automobiles in a variety of fields without beinglimited to the electronic devices described in this embodiment.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in other embodiments.

(Embodiment 6)

In this embodiment, a structure of a lighting device fabricated usingthe light-emitting element which is one embodiment of the presentinvention is described with reference to FIGS. 8A to 8D.

FIGS. 8A to 8D are examples of cross-sectional views of lightingdevices. FIGS. 8A and 8B illustrate bottom-emission lighting devices inwhich light is extracted from the substrate side, and FIGS. 8C and 8Dillustrate top-emission lighting devices in which light is extractedfrom the sealing substrate side.

A lighting device 4000 illustrated in FIG. 8A includes a light-emittingelement 4002 over a substrate 4001. In addition, the lighting device4000 includes a substrate 4003 with unevenness on the outside of thesubstrate 4001. The light-emitting element 4002 includes a firstelectrode 4004, an EL layer 4005, and a second electrode 4006.

The first electrode 4004 is electrically connected to an electrode 4007,and the second electrode 4006 is electrically connected to an electrode4008. In addition, an auxiliary wiring 4009 electrically connected tothe first electrode 4004 may be provided. Note that an insulating layer4010 is formed over the auxiliary wiring 4009.

The substrate 4001 and a sealing substrate 4011 are bonded to each otherby a sealant 4012. A desiccant 4013 is preferably provided between thesealing substrate 4011 and the light-emitting element 4002. Thesubstrate 4003 has the unevenness illustrated in FIG. 8A, whereby theextraction efficiency of light emitted from the light-emitting element4002 can be increased.

Instead of the substrate 4003, a diffusion plate 4015 may be provided onthe outside of a substrate 4001 as in a lighting device 4100 illustratedin FIG. 8B.

A lighting device 4200 illustrated in FIG. 8C includes a light-emittingelement 4202 over a substrate 4201. The light-emitting element 4202includes a first electrode 4204, an EL layer 4205, and a secondelectrode 4206.

The first electrode 4204 is electrically connected to an electrode 4207,and the second electrode 4206 is electrically connected to an electrode4208. An auxiliary wiring 4209 electrically connected to the secondelectrode 4206 may be provided. An insulating layer 4210 may be providedunder the auxiliary wiring 4209.

The substrate 4201 and a sealing substrate 4211 with unevenness arebonded to each other by a sealant 4212. A barrier film 4213 and aplanarization film 4214 may be provided between the sealing substrate4211 and the light-emitting element 4202. The sealing substrate 4211 hasthe unevenness illustrated in FIG. 8C, whereby the extraction efficiencyof light emitted from the light-emitting element 4202 can be increased.

Instead of the sealing substrate 4211, a diffusion plate 4215 may beprovided over the light-emitting element 4202 as in a lighting device4300 illustrated in FIG. 8D.

Note that the EL layers 4005 and 4205 in this embodiment can include theorganometallic complex which is one embodiment of the present invention.In that case, a lighting device with low power consumption can beprovided.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in other embodiments.

(Embodiment 7)

In this embodiment, examples of a lighting device to which thelight-emitting device of one embodiment of the present invention isapplied are described with reference to FIG. 9.

FIG. 9 illustrates an example in which the light-emitting device is usedas an indoor lighting device 8001. Since the light-emitting device canhave a large area, it can be used for a lighting device having a largearea. In addition, with the use of a housing with a curved surface, alighting device 8002 in which a light-emitting region has a curvedsurface can also be obtained. A light-emitting element included in thelight-emitting device described in this embodiment is in a thin filmform, which allows the housing to be designed more freely. Thus, thelighting device can be elaborately designed in a variety of ways. Inaddition, a wall of the room may be provided with a lighting device8003.

Besides the above examples, when the light-emitting device is used aspart of furniture in a room, a lighting device that functions as thefurniture can be obtained.

As described above, a variety of lighting devices that include thelight-emitting device can be obtained. Note that these lighting devicesare also embodiments of the present invention.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in other embodiments.

(Embodiment 8)

In this embodiment, touch panels including a light-emitting element ofone embodiment of the present invention or a light-emitting device ofone embodiment of the present invention are described with reference toFIGS. 10A and 10B, FIGS. 11A and 11B, FIGS. 12A and 12B, FIGS. 13A and13B, and FIG. 14.

FIGS. 10A and 10B are perspective views of a touch panel 2000. Note thatFIGS. 10A and 10B illustrate typical components of the touch panel 2000for simplicity.

The touch panel 2000 includes a display portion 2501 and a touch sensor2595 (see FIG. 10B). Furthermore, the touch panel 2000 includes asubstrate 2510, a substrate 2570, and a substrate 2590. Note that thesubstrate 2510, the substrate 2570, and the substrate 2590 each haveflexibility.

The display portion 2501 includes a plurality of pixels over thesubstrate 2510, and a plurality of wirings 2511 through which signalsare supplied to the pixels. The plurality of wirings 2511 are led to aperipheral portion of the substrate 2510, and part of the plurality ofwirings 2511 forms a terminal 2519. The terminal 2519 is electricallyconnected to an FPC 2509(1).

The substrate 2590 includes the touch sensor 2595 and a plurality ofwirings 2598 electrically connected to the touch sensor 2595. Theplurality of wirings 2598 are led to a peripheral portion of thesubstrate 2590, and part of the plurality of wirings 2598 forms aterminal 2599. The terminal 2599 is electrically connected to an FPC2509(2). Note that in FIG. 10B, electrodes, wirings, and the like of thetouch sensor 2595 provided on the back side of the substrate 2590 (theside facing the substrate 2510) are indicated by solid lines forclarity.

As the touch sensor 2595, a capacitive touch sensor can be used, forexample. Examples of the capacitive touch sensor are a surfacecapacitive touch sensor, a projected capacitive touch sensor, and thelike.

Examples of the projected capacitive touch sensor are a self-capacitivetouch sensor, a mutual capacitive touch sensor, and the like, whichdiffer mainly in the driving method. The use of a mutual capacitivetouch sensor is preferable because multiple points can be sensedsimultaneously.

First, an example of using a projected capacitive touch sensor isdescribed with reference to FIG. 10B. Note that in the case of aprojected capacitive touch sensor, a variety of sensors that can sensethe closeness or the contact of a sensing target such as a finger can beused.

The projected capacitive touch sensor 2595 includes electrodes 2591 andelectrodes 2592. The electrodes 2591 are electrically connected to anyof the plurality of wirings 2598, and the electrodes 2592 areelectrically connected to any of the other wirings 2598. The electrodes2592 each have a shape of a plurality of quadrangles arranged in onedirection with one corner of a quadrangle connected to one corner ofanother quadrangle with a wiring 2594 in one direction, as illustratedin FIGS. 10A and 10B. In the same manner, the electrodes 2591 each havea shape of a plurality of quadrangles arranged with one corner of aquadrangle connected to one corner of another quadrangle; however, thedirection in which the electrodes 2591 are connected is a directioncrossing the direction in which the electrodes 2592 are connected. Notethat the direction in which the electrodes 2591 are connected and thedirection in which the electrodes 2592 are connected are not necessarilyperpendicular to each other, and the electrodes 2591 may be arranged tointersect with the electrodes 2592 at an angle greater than 0° and lessthan 90°.

The intersecting area of the wiring 2594 and one of the electrodes 2592is preferably as small as possible. Such a structure allows a reductionin the area of a region where the electrodes are not provided, reducingunevenness in transmittance. As a result, unevenness in the luminance oflight from the touch sensor 2595 can be reduced.

Note that the shapes of the electrodes 2591 and the electrodes 2592 arenot limited to the above-mentioned shapes and can be any of a variety ofshapes. For example, the plurality of electrodes 2591 may be provided sothat a space between the electrodes 2591 are reduced as much aspossible, and the plurality of electrodes 2592 may be provided with aninsulating layer sandwiched between the electrodes 2591 and theelectrodes 2592. In that case, between two adjacent electrodes 2592, adummy electrode which is electrically insulated from these electrodes ispreferably provided, whereby the area of a region having a differenttransmittance can be reduced.

Next, the touch panel 2000 is described in detail with reference toFIGS. 11A and 11B. FIGS. 11A and 11B are cross-sectional views takenalong the dashed-dotted line X1-X2 in FIG. 10A.

The touch sensor 2595 includes the electrodes 2591 and the electrodes2592 that are provided in a staggered arrangement on the substrate 2590,an insulating layer 2593 covering the electrodes 2591 and the electrodes2592, and the wiring 2594 that electrically connects the adjacentelectrodes 2591 to each other.

An adhesive layer 2597 is provided below the wiring 2594. The substrate2590 is attached to the substrate 2570 with the adhesive layer 2597 sothat the touch sensor 2595 overlaps with the display portion 2501.

The electrodes 2591 and the electrodes 2592 are formed using alight-transmitting conductive material. As a light-transmittingconductive material, a conductive oxide such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded can be used. Note that a film containing graphene may be used aswell. The film including graphene can be formed, for example, byreducing a film containing graphene oxide. As a reducing method, amethod with application of heat or the like can be employed.

For example, the electrodes 2591 and the electrodes 2592 may be formedby depositing a light-transmitting conductive material on the substrate2590 by a sputtering method and then removing an unnecessary portion byany of various patterning techniques such as a photolithography method.

Examples of a material for the insulating layer 2593 are a resin such asacrylic or epoxy resin, a resin having a siloxane bond, and an inorganicinsulating material such as silicon oxide, silicon oxynitride, oraluminum oxide.

The wiring 2594 is formed in an opening provided in the insulating layer2593, whereby the adjacent electrodes 2591 are electrically connected toeach other. A light-transmitting conductive material can be favorablyused for the wiring 2594 because the aperture ratio of the touch panelcan be increased. Moreover, a material having higher conductivity thanthe electrodes 2591 and 2592 can be favorably used for the wiring 2594because electric resistance can be reduced.

Through the wiring 2594, a pair of electrodes 2591 is electricallyconnected to each other. Between the pair of electrodes 2591, theelectrode 2592 is provided.

One wiring 2598 is electrically connected to any of the electrodes 2591and 2592. Part of the wiring 2598 serves as a terminal. For the wiring2598, a metal material such as aluminum, gold, platinum, silver, nickel,titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, orpalladium or an alloy material containing any of these metal materialscan be used.

Through the terminal 2599, the wiring 2598 and the FPC 2509(2) areelectrically connected to each other. The terminal 2599 can be formedusing any of various kinds of anisotropic conductive films (ACF),anisotropic conductive pastes (ACP), and the like.

The adhesive layer 2597 has a light-transmitting property. For example,a thermosetting resin or an ultraviolet curable resin can be used;specifically, a resin such as an acrylic-based resin, a urethane-basedresin, an epoxy-based resin, or a siloxane-based resin can be used.

The display portion 2501 includes a plurality of pixels arranged in amatrix. Each of the pixels includes a display element and a pixelcircuit for driving the display element.

For the substrate 2510 and the substrate 2570, for example, a flexiblematerial having a vapor permeability of 1×10⁻⁵ g/(m²·day) or lower,preferably 1×10⁻⁶ g/(m²·day) or lower can be favorably used. Note thatmaterials whose thermal expansion coefficients are substantially equalto each other are preferably used for the substrate 2510 and thesubstrate 2570. For example, the coefficient of linear expansion of thematerials are preferably lower than or equal to 1×10⁻³/K, furtherpreferably lower than or equal to 5×10⁻⁵/K, and still further preferablylower than or equal to 1×10⁻⁵/K.

A sealing layer 2560 preferably has a higher refractive index than theair.

The display portion 2501 includes a pixel 2502R. The pixel 2502Rincludes a light-emitting module 2580R.

The pixel 2502R includes a light-emitting element 2550R and a transistor2502 t which can supply electric power to the light-emitting element2550R. Note that the transistor 2502 t functions as part of the pixelcircuit. The light-emitting module 2580R includes the light-emittingelement 2550R and a coloring layer 2567R.

The light-emitting element 2550R includes a lower electrode, an upperelectrode, and an EL layer between the lower electrode and the upperelectrode.

In the case where the sealing layer 2560 is provided on the lightextraction side, the sealing layer 2560 is in contact with thelight-emitting element 2550R and the coloring layer 2567R.

The coloring layer 2567R overlaps with the light-emitting element 2550R.Thus, part of light emitted from the light-emitting element 2550R passesthrough the coloring layer 2567R and is emitted to the outside of thelight-emitting module 2580R, as indicated by an arrow in the figure.

The display portion 2501 includes a light-blocking layer 2567BM on thelight extraction side. The light-blocking layer 2567BM is provided so asto surround the coloring layer 2567R.

The display portion 2501 includes an anti-reflective layer 2567 p in aregion overlapping with pixels. As the anti-reflective layer 2567 p, acircular polarizing plate can be used, for example.

An insulating layer 2521 is provided in the display portion 2501. Theinsulating layer 2521 covers the transistor 2502 t. With the insulatinglayer 2521, unevenness caused by the pixel circuit is reduced. Theinsulating layer 2521 may serve also as a layer for preventing diffusionof impurities. This can prevent a reduction in the reliability of thetransistor 2502 t or the like due to diffusion of impurities.

The light-emitting element 2550R is formed above the insulating layer2521. A partition 2528 is provided so as to overlap with end portions ofthe lower electrode in the light-emitting element 2550R. Note that aspacer for controlling the distance between the substrate 2510 and thesubstrate 2570 may be provided over the partition 2528.

A scan line driver circuit 2503 g(1) includes a transistor 2503 t and acapacitor 2503 c. Note that the driver circuit and the pixel circuitscan be found in the same process over the same substrate.

Over the substrate 2510, the wirings 2511 through which a signal can besupplied are provided. Over the wirings 2511, the terminal 2519 isprovided. The FPC 2509(1) is electrically connected to the terminal2519. The FPC 2509(1) has a function of supplying signals such as animage signal and a synchronization signal. Note that a printed wiringboard (PWB) may be attached to the FPC 2509(1).

For the display portion 2501, transistors with a variety of structurescan be used. In the example of FIG. 11A, bottom-gate transistors areused. In each of the transistor 2502 t and the transistor 2503 tillustrated in FIG. 11A, a semiconductor layer including an oxidesemiconductor can be used for a channel region. Alternatively, in eachof the transistor 2502 t and the transistor 2503 t, a semiconductorlayer including amorphous silicon can be used for a channel region.Further alternatively, in each of the transistor 2502 t and thetransistor 2503 t, a semiconductor layer including polycrystallinesilicon which is obtained by a crystallization process such as laserannealing can be used for a channel region.

FIG. 11B illustrates the structure of the display portion 2501 in whichtop-gate transistors are used.

In the case of a top-gate transistor, a semiconductor layer includingpolycrystalline silicon, a single crystal silicon film that istransferred from a single crystal silicon substrate, or the like may beused for a channel region as well as the above semiconductor layers thatcan be used for a bottom-gate transistor.

Next, a touch panel having a structure different from that illustratedin FIGS. 11A and 11B is described with reference to FIGS. 12A and 12B.

FIGS. 12A and 12B are cross-sectional views of the touch panel 2001. Inthe touch panel 2001 illustrated in FIGS. 12A and 12B, the position ofthe touch sensor 2595 relative to the display portion 2501 is differentfrom that in the touch panel 2000 illustrated in FIGS. 11A and 11B.Different structures are described in detail below, and the abovedescription of the touch panel 2000 can be referred to for the othersimilar structures.

The coloring layer 2567R overlaps with the light-emitting element 2550R.The light-emitting element 2550R illustrated in FIG. 12A emits light tothe side where the transistor 2502 t is provided. Accordingly, part oflight emitted from the light-emitting element 2550R passes through thecoloring layer 2567R and is emitted to the outside of the light-emittingmodule 2580R, as indicated by an arrow in FIG. 12A.

The display portion 2501 includes the light-blocking layer 2567BM on thelight extraction side. The light-blocking layer 2567BM is provided so asto surround the coloring layer 2567R.

The touch sensor 2595 is provided on the substrate 2510 side of thedisplay portion 2501 (see FIG. 12A).

The display portion 2501 and the touch sensor 2595 are attached to eachother with the adhesive layer 2597 provided between the substrate 2510and the substrate 2590.

For the display portion 2501, transistors with a variety of structurescan be used. In the example of FIG. 12A, a bottom-gate transistor isused. In the example of FIG. 12B, a top-gate transistor is used.

An example of a driving method of the touch panel is described withreference to FIGS. 13A and 13B.

FIG. 13A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. FIG. 13A illustrates a pulse voltage outputcircuit 2601 and a current sensing circuit 2602. Note that in theexample of FIG. 13A, six wirings X1-X6 represent electrodes 2621 towhich a pulse voltage is supplied, and six wirings Y1-Y6 representelectrodes 2622 that sense a change in current. FIG. 13A alsoillustrates a capacitor 2603 which is formed in a region where theelectrodes 2621 and 2622 overlap with each other. Note that functionalreplacement between the electrodes 2621 and 2622 is possible.

The pulse voltage output circuit 2601 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to X6. By application of apulse voltage to the wirings X1 to X6, an electric field is generatedbetween the electrodes 2621 and 2622 of the capacitor 2603. When theelectric field between the electrodes is shielded, for example, a changeoccurs in the capacitor 2603 (mutual capacitance). The approach orcontact of a sensing target can be sensed by utilizing this change.

The current sensing circuit 2602 is a circuit for sensing changes incurrent flowing through the wirings Y1 to Y6 that are caused by thechange in mutual capacitance in the capacitor 2603. No change in currentvalue is sensed in the wirings Y1 to Y6 when there is no approach orcontact of a sensing target, whereas a decrease in current value issensed when mutual capacitance is decreased owing to the approach orcontact of a sensing target. Note that an integrator circuit or the likeis used for sensing of current.

FIG. 13B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 13A. In FIG. 13B,sensing of a sensing target is performed in all the rows and columns inone frame period. FIG. 13B shows a period when a sensing target is notsensed (not touched) and a period when a sensing target is sensed(touched). Sensed current values of the wirings Y1 to Y6 are shown asthe waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1 to X6, and thewaveforms of the wirings Y1 to Y6 change in accordance with the pulsevoltage. When there is no approach or contact of a sensing target, thewaveforms of the wirings Y1 to Y6 change in accordance with changes inthe voltages of the wirings X1 to X6. The current value is decreased atthe point of approach or contact of a sensing target and accordingly thewaveform of the voltage value changes. By sensing a change in mutualcapacitance in this manner, the approach or contact of a sensing targetcan be sensed.

Although FIG. 13A illustrates a passive touch sensor in which only thecapacitor 2603 is provided at the intersection of wirings as a touchsensor, an active touch sensor including a transistor and a capacitormay be used. FIG. 14 is a sensor circuit included in an active touchsensor.

The sensor circuit illustrated in FIG. 14 includes the capacitor 2603, atransistor 2611, a transistor 2612, and a transistor 2613.

A signal G2 is input to a gate of the transistor 2613. A voltage VRES isapplied to one of a source and a drain of the transistor 2613, and oneelectrode of the capacitor 2603 and a gate of the transistor 2611 areelectrically connected to the other of the source and the drain of thetransistor 2613. One of a source and a drain of the transistor 2611 iselectrically connected to one of a source and a drain of the transistor2612, and a voltage VSS is applied to the other of the source and thedrain of the transistor 2611. A signal G1 is input to a gate of thetransistor 2612, and a wiring ML is electrically connected to the otherof the source and the drain of the transistor 2612. The voltage VSS isapplied to the other electrode of the capacitor 2603.

Next, the operation of the sensor circuit illustrated in FIG. 14 isdescribed. First, a potential for turning on the transistor 2613 issupplied as the signal G2, and a potential with respect to the voltageVRES is thus applied to the node n connected to the gate of thetransistor 2611. Then, a potential for turning off the transistor 2613is applied as the signal G2, whereby the potential of the node n ismaintained. Then, mutual capacitance of the capacitor 2603 changes owingto the approach or contact of a sensing target such as a finger, andaccordingly the potential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 2612 issupplied as the signal G1. A current flowing through the transistor2611, that is, a current flowing through the wiring ML is changed inaccordance with the potential of the node n. By sensing this current,the approach or contact of a sensing target can be sensed.

In each of the transistors 2611, 2612, and 2613, an oxide semiconductorlayer is preferably used as a semiconductor layer in which a channelregion is formed. Such a transistor is preferably used as the transistor2613, in particular, so that the potential of the node n can be held fora long time and the frequency of operation of resupplying VRES to thenode n (refresh operation) can be reduced.

At least part of this embodiment can be implemented in combination withany of other embodiments described in this specification as appropriate.

EXAMPLE 1 Synthetic Example 1

In this example, a synthesis method of{6-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl-κN²)]-[5-(pyridin-2-yl-κN)-5,7-dihydro-indolo[2,3-b]carbazole-5,7-diyl-κC⁶]phenyl-κC}platinum(II)(Abbreviation:[Pt(ptzICz)]) which is an organometallic complex of oneembodiment of the present invention represented by the structuralformula (100) in Embodiment 1 is described. Note that a structure of[Pt(ptzICz)] is shown below.

Step 1: Synthesis of N-3-bromobenzoyl-N-2-methylbenzoylhydrazide

25.0 g (166 mmol) of o-toluyl hydrazide and 120 mL ofN-methyl-2-pyrrolidinone (NMP) were added to a 500-mL three-neck flask.The atmosphere in the flask was replaced with nitrogen. Then, themixture was stirred while being cooled with ice. To this mixed solution,a mixed solution of 36.5 g (166 mmol) of 3-bromobenzoyl chloride and 50mL of NMP was slowly added dropwise, and the mixture was stirred for 20hours. After reaction for the predetermined time, this reacted solutionwas slowly added to 300 mL of water, so that a white solid wasprecipitated. The precipitated solid was subjected to ultrasoniccleaning in which water and 1M hydrochloric acid were used alternately.After that, ultrasonic cleaning using ethanol was performed, so that39.5 g of a white solid was obtained in a yield of 71%. By a nuclearmagnetic resonance (NMR) method, the obtained white solid was identifiedas N-3-bromobenzoyl-N′-2-methylbenzoylhydrazide. The synthesis scheme ofStep 1 is shown in (a-0).

Step 2: Synthesis ofN-chloro-3-bromophenylmethylidene-N′-chloro-2-methylphenylmethylidenehydrazone

39.5 g (119 mmol) of N-3-bromobenzoyl-N-2-methylbenzoylhydrazide and 800mL of toluene were put into a 2000-mL three-neck flask. To this mixedsolution, 75.0 g (360 mmol) of phosphorus pentachloride was added andthe mixture was heated and stirred at 120° C. for 8 hours under anitrogen stream. After reaction for the predetermined time, this reactedsolution was slowly added to 400 mL of water, and the mixture wasstirred at room temperature for 30 minutes. After the stirring, theprecipitated solid was removed by filtration, the obtained filtrate wasseparated to an organic layer and an aqueous layer, and the aqueouslayer was extracted with toluene. The extracted solution obtained andthe organic layer were collected, the organic layer was slowly added to400 mL of a 2M potassium hydroxide solution, and the mixture was stirredat room temperature for 48 hours. This mixture was separated to anorganic layer and an aqueous layer, and the aqueous layer was extractedwith toluene. The obtained solution of the extract and the organic layerwere combined and washed with saturated saline. After washing, anhydrousmagnesium sulfate was added to the organic layer for drying, and theresulting mixture was subjected to gravity filtration to give afiltrate. The obtained filtrate was concentrated to give an oilysubstance. The obtained oily substance was purified by silica columnchromatography. Toluene was used as a developing solvent. The obtainedfraction was concentrated to give 42.6 g of a yellow solid in 97% yield.By a nuclear magnetic resonance (NMR) method, the obtained yellow solidwas identified asN-chloro-3-bromophenylmethylidene-N′-chloro-2-methylphenylmethylidenehydrazone.The synthesis scheme of Step 2 is shown in (b-0).

Step 3: Synthesis of3-(3-bromophenyl)-4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazole

30.0 g (81.0 mmol) ofN-chloro-3-bromophenylmethylidene-N′-chloro-2-methylphenylmethylidenehydrazone,1 g (243 mmol) of 2,6-diisopropylaniline, and 250 mL ofN,N-dimethylaniline were put into a 1000-mL three-neck flask, and thismixture was heated and stirred at 160° C. for 13 hours under a nitrogenstream. After reaction for the predetermined time, this reacted solutionwas put into 3M hydrochloric acid and stirred for 30 minutes. Toluenewas added therein, and the aqueous layer was extracted with toluene. Thesolution of the extract and the organic layer were combined, and washedwith water, a saturated aqueous solution of sodium hydrogen carbonate,and saturated saline, and anhydrate magnesium sulfate was added into theorganic layer for drying. The obtained mixture was gravity-filtered, andthe filtrate was concentrated to give an oily substance. The obtainedoily substance was purified by silica column chromatography. As thedeveloping solvent, a 5:1 hexane-ethyl acetate mixed solvent was used.The resulting fraction was concentrated to give a white solid. The solidwas recrystallized with a mixed solvent of ethyl acetate and hexane togive 17.6 g of a white solid in a yield of 46%. By a nuclear magneticresonance (NMR) method, the obtained white solid was identified as3-(3-bromophenyl)-4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazole.The synthesis scheme of Step 3 is shown in (c-0).

Step 4: Synthesis of 5,7-dihydro-5-(2-pyridyl)-indolo[2,3-b]carbazole

1.0 g (3.9 mmol) of 5,7-dihydro-indolo[2,3-b]carbazole, 0.80 g (3.9mmol) of 2-iodopyridine, 0.14 g (0.78 mmol) of 1,10-phenanthroline, and2.5 g (7.8 mmol) of cesium carbonate were put into a reaction container,and the atmosphere in the flask was replaced with nitrogen. 8 mL ofN,N-dimethylformamide was added to this mixture, the mixture was stirredto be degassed while the pressure in the flask was reduced. After that,the atmosphere in the flask was replaced with nitrogen, 0.074 g (0.39mmol) of copper iodide was added, and the mixture was heated at 100° C.for 11.5 hours. Chloroform was added to the reactive mixture and themixture was subjected to filtration through celite. The obtainedfiltrate was concentrated to give an oily substance. The obtained oilysubstance was purified by silica column chromatography. As thedeveloping solvent, a 3:1 hexane-ethyl acetate mixed solvent was used.The obtained fraction was concentrated to obtain a solid. To theobtained solid was added methanol, irradiation with ultrasonic waves wasperformed, and a solid was removed by suction filtration. The obtainedfiltrate was concentrated to give 0.37 g of a white solid, which was atarget substance, in a yield of 28%. By a nuclear magnetic resonance(NMR) method, the obtained white solid was identified as5,7-dihydro-5-(2-pyridyl)-indolo[2,3-b]carbazole. The synthesis schemeof Step 4 is shown in (d-0).

Step 5: Synthesis of7-{3-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl]phenyl}-5-(2-pyridyl)-5,7-dihydro-indolo[2,3-b]carbazole(Abbreviation: H₂ptzICz)

1.3 g (2.7 mmol) of2-(3-bromophenyl)-4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazole,0.91 g (2.7 mmol) of 5,7-dihydro-5-(2-pyridyl)-indolo[2,3-b]carbazole,0.91 g (8.1 mmol) of potassium-tert-butoxide, 0.067 g (0.162 mmol) of2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (S-Phos), and 100 mL ofxylene were put into a 300-mL three-neck flask, and the atmosphere inthe flask was replaced with nitrogen. After that, the mixture wasstirred to be degassed while the pressure in the flask was reduced.After that, the atmosphere in the flask was replaced with nitrogen,0.074 g (0.081 mmol) of tris(dibenzylideneacetone)dipalladium(0) wasadded, and the mixture was stirred at 120° C. for 7.5 hours under anitrogen stream. Toluene was added to the reactive mixture and themixture was subjected to filtration through celite. The obtainedfiltrate was concentrated to give an oily substance. The obtained oilysubstance was purified by silica column chromatography. As a developingsolvent, a 1:1 hexane-ethyl acetate mixed solvent was used. The obtainedfraction was concentrated to give 0.64 g of a white solid in 33% yield.By a nuclear magnetic resonance (NMR) method, the obtained white solidwas identified as7-{3-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl]phenyl}-5-(2-pyridyl)-5,7-dihydro-indolo[2,3-b]carbazole.A synthesis scheme of Step 5 is shown in (e-0).

Step 6: Synthesis of{6-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl-κN²)]-2-[5-(pyridin-2-yl-κN)-5,7-dihydro-indolo[2,3-b]carbazole-5,7-diyl-κC⁶]phenyl-κC}platinum(II)(Abbreviation: [Pt(ptzICz)])

0.64 g (0.88 mmol) of7-{3-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl)]phenyl}-5-(2-pyridyl)-5,7-dihydro-indolo[2,3-b]carbazole,0.37 g (0.88 mmol) of potassium chloroplatinate, 0.028 g of (0.088 mmol)of tetrabutylammonium bromide, and 60 mL of glacial acetic acid were putinto a 300-mL recovery flask, and this mixture was stirred at 120° C.for 56 hours under a nitrogen stream. 60 mL of water was added to thereactive mixture, and the mixture was stirred for 30 minutes andsubjected to suction filtration to give a solid. Tolune was added to theobtained solid and the mixture was filtered through a filter aid inwhich Celite, alumina, Florisil and Celite were stacked in this order.The obtained filtrate was condensed to obtain a solid. The obtainedsolid was recrystallized with a mixed solvent of ethyl acetate andhexane to give 0.22 g of an yellow solid in a yield of 27%. 0.21 g ofthe obtained solid was purified by a train sublimation method. Thepurification was conducted by heating of the solid at 320° C. for 16hours under a pressure of 2.6 Pa with a flow rate of argon gas of 5.0mL/min. After the purification, 0.15 g of [Pt(ptzICz)] which was theobject of the synthesis was obtained at a collection rate of 71%. Thesynthesis scheme of Step 6 is illustrated in (f-0).

Measurements were performed on the protons (¹H) of the yellow solid thatwas obtained in Step 6 by a nuclear magnetic resonance (NMR) method. Theobtained values are shown below. FIG. 15 shows the ¹H-NMR chart. Theseresults revealed that [Pt(ptzICz)], the organometallic complex accordingto the present invention which is represented by the above structuralformula (100), was obtained in Synthesis Example 1.

¹H-NMR. δ (CDCl₃): 0.98 (dd, 12H), 2.60-2.68 (m, 2H), 2.71 (s, 3H), 6.22(d, 1H), 6.97-7.05 (m, 3H), 7.14 (t, 1H), 7.28-7.47 (m, 8H), 7.61 (t,1H), 7.95 (t, 1H), 8.04-8.06 (m, 1H), 8.24-8.35 (m, 5H), 8.60 (s, 1H),10.78 (d, 1H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as absorption spectrum) and an emission spectrum of adichloromethane solution of [Pt(ptzICz)] were measured. The absorptionspectrum was measured with an ultraviolet-visible lightspectrophotometer (V550 type, produced by JASCO Corporation) at roomtemperature in the state where the dichloromethane solution (0.0010mmol/L) was in a quartz cell. In addition, the measurement of theemission spectrum was performed at room temperature in such a mannerthat an absolute PL quantum yield measurement system (C11347-01manufactured by Hamamatsu Photonics K. K.) was used and the deoxidizeddichloromethane solution (0.0010 mmol/L) was sealed in a quartz cellunder a nitrogen atmosphere in a glove box (LABstar M13 (1250/780)manufactured by Bright Co., Ltd.). FIG. 16A shows measurement results ofthe absorption spectrum and the emission spectrum. The horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In the absorption spectrum shown inFIG. 16A, absorption considered to be transition from the singlet groundstate to the triplet excited state is shown in FIG. 16B. The horizontalaxis represents wavelength and the vertical axis represents absorptionintensity (molar absorption coefficient L/(mol·cm)). Note that theabsorption spectrum in FIGS. 16A and 16B, is a result obtained bysubtraction of a measured absorption spectrum of only dichloromethanethat was put in a quartz cell from the measured absorption spectrum ofthe dichloromethane solution (0.0010 mmol/L) in a quartz cell. Thequantum yield was 0.92.

As shown in FIG. 16A, the platinum complex [Pt(ptzICz)] has an emissionpeak at 510 nm, and green light emission from the dichloromethane wasobserved. Furthermore, as shown in FIG. 16B, in the platinum complex[Pt(ptzICz)], strong absorption based on transition from the singletground state to the triplet excited state was observed at 470 nm to 550nm.

Next, [Pt(ptzICz)] obtained in this example was subjected to a MSanalysis by liquid chromatography mass spectrometry (LC/MS).

In the LC/MS, liquid chromatography (LC) separation was carried out withACQUITY UPLC (registered trademark) which was produced by WatersCorporation and mass spectrometry (MS) was carried out with Xevo G2 TofMS (produced by Waters Corporation). ACQUITY UPLC BEH C8 (2.1×100 mm,1.7 μm) was used as a column for the LC separation, and the columntemperature was 40° C. Acetonitrile was used for Mobile Phase A and a0.1% formic acid aqueous solution was used for Mobile Phase B.Furthermore, a sample was prepared in such a manner that [Pt(ptzICz)]was dissolved in chloroform at a given concentration and the mixture wasdiluted with acetonitrile. The injection amount was 5.0 μL.

In the LC separation, a gradient method in which the composition ofmobile phases is changed was employed. The ratio of Mobile Phase A toMobile Phase B was 75:25 for 0 to 1 minute after the start of themeasurement, and then the composition was changed such that the ratio ofMobile Phase A to Mobile Phase B after 10 minutes from the start of themeasurement was 95:5. The composition was changed linearly.

In the MS analysis, ionization was carried out by an electrosprayionization (EST) method. At this time, the capillary voltage and thesample cone voltage were set to 3.0 kV and 30 V, respectively, anddetection was performed in a positive mode. A component with m/z of919.30 that underwent the ionization under the above-describedconditions was collided with an argon gas in a collision cell todissociate into product ions. Energy (collision energy) for thecollision with argon was 70 eV. A mass range for the measurement wasm/z=100-1200. The detection result of the dissociated product ions bytime-of-flight (TOF) MS are shown in FIG. 17.

The results in FIG. 17 show that product ions of [Pt(ptzICz)] aredetected mainly around m/z=903, m/z=888, m/z=875, m/z=859, m/z=844,m/z=771, m/z=757, m/z=627, and m/z=221. The results in FIG. 17 showcharacteristics derived from [Pt(ptzICz)] and can thus be regarded asimportant data in identification of [Pt(ptzICz)] contained in a mixture.

EXAMPLE 2

In this example, a light-emitting element 1 and a light-emitting element2 each including [Pt(ptzICz)] (represented by the structural formula(100)) which is an organometallic complex of one embodiment of thepresent invention were fabricated. Note that the fabrication of thelight-emitting elements is described with reference to FIG. 18. Chemicalformulae of materials used in this example are shown below.

<<Fabrication of Light-Emitting Element>>

First, indium tin oxide (ITO) containing silicon oxide was depositedover a glass substrate 900 by a sputtering method, whereby a firstelectrode 901 functioning as an anode was formed. The thickness of thefirst electrode 901 was 70 nm and the electrode area was 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate 900, UV ozone treatment was performed for 370 seconds afterwashing of a surface of the substrate with water and baking that wasperformed at 200° C. for 1 hour.

After that, the substrate 900 was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 1×10⁻⁴Pa, and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus. Then, the substrate900 was cooled down for approximately 30 minutes.

Next, the substrate 900 over which the first electrode 901 was formedwas fixed to a holder provided inside a vacuum evaporation apparatus sothat the surface over which the first electrode was formed faceddownward. In this example, a case will be described in which ahole-injection layer 911, a hole-transport layer 912, a light-emittinglayer 913, an electron-transport layer 914, and an electron-injectionlayer 915 which are included in an EL layer 902 are sequentially formedby a vacuum evaporation method.

After reducing the pressure of the vacuum evaporation apparatus to1×10⁻⁴ Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation:DBT3P-II) and molybdenum oxide were co-evaporated at a mass ratio of 4:2(DBT3P-II: molybdenum oxide), whereby the hole-injection layer 911 wasformed over the first electrode 901. The thickness was set to 60 nm.Note that a co-evaporation method is an evaporation method in which aplurality of different substances is concurrently vaporized fromrespective different evaporation sources.

Then, 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation:PCCP) was deposited by evaporation to a thickness of 20 nm, whereby thehole-transport layer 912 was formed.

Next, the light-emitting layer 913 was formed on the hole-transportlayer 912.

In the case of the light-emitting element 1,9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP),3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy),and [Pt(ptzICz)] are co-evaporated to a thickness of 20 nm with a massratio of PCCP to 35DczPPy and [Pt(ptzICz)] being 0.5:0.5:0.05, and thenare co-evaporated to a thickness of 20 nm with a mass ratio of PCCP to35DczPPy and [Pt(ptzICz)] being 0.8:0.2:0.05, whereby the light-emittinglayer 913 having a stacked-layer structure was formed with a thicknessof 40 nm.

In the case of the light-emitting element 2, PCCP,9,9′-(pyrimidine-4,6-diyldi-3,1-phenylene)bis(9H-carbazole)(abbreviation: 4,6mCzP2Pm), and [Pt(ptzICz)] are co-evaporated to athickness of 20 nm with a mass ratio of PCCP to 4,6mCzP2Pm and[Pt(ptzICz)] being 0.5:0.5:0.05, and then are co-evaporated to athickness of 20 nm with a mass ratio of PCCP to 4,6mCzP2Pm and[Pt(ptzICz)] being 0.8:0.2:0.05, whereby the light-emitting layer 913having a stacked-layer structure was formed with a thickness of 40 nm.

Next, in the case of the light-emitting element 1, theelectron-transport layer 914 was formed over the light-emitting layer913 in such a manner that 35DczPPy was evaporated to a thickness of 15nm, and then Bphen was evaporated to a thickness of 15 nm. In the caseof the light-emitting element 2, the electron-transport layer 914 wasformed in such a manner that 4,6mCzP2Pm was evaporated to a thickness of20 nm, and then Bphen was evaporated to a thickness of 10 nm.

Furthermore, lithium fluoride was evaporated to a thickness of 1 nm overthe electron-transport layer 914, whereby the electron-injection layer915 was formed.

Finally, aluminum was deposited to a thickness of 200 nm over theelectron-injection layer 915, whereby a second electrode 903 functioningas a cathode was formed. Thus, the light-emitting elements 1 and 2 werefabricated. It is to be noted that an evaporation method using resistiveheating was employed for all the evaporation steps.

Element structures of the light-emitting elements 1 and 2 obtained inthe above manner are shown in Table 1.

TABLE 1 Hole- Hole- Light- Electron- First injection transport emittingElectron-transport injection Second Electrode Layer Layer Layer LayerLayer Electrode Light- ITO DBT3P- PCCP * 35DCzPPy Bphen LiF Al emitting(70 nm) II:MoOx (20 nm) (15 nm) (15 nm) (1 nm) (200 nm) Element 1 (4:260 nm) Light- ITO DBT3P- PCCP ** 4,6mCzP2Pm Bphen LiF Al emitting (70nm) II:MoOx (20 nm) (20 nm) (10 nm) (1 nm) (200 nm) Element 2 (4:2 60nm) * PCCP:35DCzPPy:[Pt(ptzICz)]\PCCP:35DCzPPy:[Pt(ptzICz)](0.5:0.5:0.05 20 nm\0.8:0.2:0.05 20 nm) **PCCP:4,6mCzP2Pm:[Pt(ptzICz)]\PCCP:4,6mCzP2Pm:[Pt(ptzICz)](0.5:0.5:0.0520 nm\0.8:0.2:0.05 20 nm)

Furthermore, the fabricated light-emitting elements were sealed in aglove box under a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealant was applied to surround the element, and at thetime of sealing, first, UV treatment was performed and then heattreatment was performed at 80° C. for 1 hour).

<<Operation Characteristics of Light-Emitting Element>>

Operation characteristics of the fabricated light-emitting elements 1and 2 were measured. It is to be noted that the measurements wereperformed at room temperature (in an atmosphere kept at 25° C.).

FIG. 19 shows current density-luminance characteristics of thelight-emitting element 1, FIG. 20 shows voltage-luminancecharacteristics of the light-emitting element 1, FIG. 21 showsluminance-current efficiency characteristics of the light-emittingelement 1, FIG. 22 shows voltage-current characteristics of thelight-emitting element 1, and FIG. 23 shows chromaticity coordinates ofthe light-emitting element 1. FIG. 25 shows current density-luminancecharacteristics of the light-emitting element 2, FIG. 26 showsvoltage-luminance characteristics of the light-emitting element 2, FIG.27 shows luminance-current efficiency characteristics of thelight-emitting element 2, FIG. 28 shows voltage-current characteristicsof the light-emitting element 2, and FIG. 29 shows chromaticitycoordinates of the light-emitting element 2.

Table 2 shows initial values of main characteristics of thelight-emitting elements 1 and 2 at a luminance of about 1000 cd/m².

TABLE 2 External Currnt Current Power Quantum Voltage Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light- 5.0 0.068 1.7 (0.33,0.62) 1100 66 41 18 emitting Element 1 Light- 3.2 0.064 1.6 (0.33, 0.62)1100 66 65 19 emitting Element 2

FIG. 24 shows an emission spectrum when a current at a current densityof 1.7 mA/cm² was supplied to the light-emitting element 1, and FIG. 30shows an emission spectrum when a current at a current density of 1.6mA/cm² was supplied to the light-emitting element 2. The emissionspectrum of the light-emitting element 1 has peaks at around 514 nm andaround 549 nm in FIG. 24, and the emission spectrum of thelight-emitting element 2 has peaks at around 513 nm and around 546 nm inFIG. 30. Accordingly, it is suggested that the peaks are derived fromgreen light emission of the organometallic complex, [Pt(ptzICz)], usedin the EL layer of each of the light-emitting elements 1 and 2.

This application is based on Japanese Patent Application serial no.2015-102410 filed with Japan Patent Office on May 20, 2015, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A light-emitting element comprising: an EL layerbetween a pair of electrodes, wherein the EL layer comprises alight-emitting layer, and wherein the light-emitting layer comprises anorganometallic complex represented by a formula (G1-1),

wherein M represents Pt or Pd, and each of R¹ to R¹⁶ independentlyrepresents any one of hydrogen, an alkyl group having 1 to 6 carbonatoms, and a substituted or unsubstituted aryl group having 6 to 13carbon atoms, wherein a ring A represents a triazole ring, and whereinthe light-emitting element emits green light.
 2. The light-emittingelement according to claim 1, wherein when the ring A is represented bya formula (α), the foimula (α) is any one of a formula (α-1), a formula(α-2), a formula (α-3), and a formula (α-4) below,

wherein each of R²¹ to R²⁸ independently represents any one of hydrogen,an alkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted aryl group having 6 to 13 carbon atoms.
 3. Thelight-emitting element according to claim 1, wherein the organometalliccomplex is represented by a formula (100) below.


4. The light-emitting element according to claim 1, wherein thelight-emitting layer comprises a guest material and a host material, andwherein the guest material is the organometallic complex represented bythe formula (G1-1).
 5. A light-emitting device comprising: thelight-emitting element according to claim 1; and any one of a transistorand a substrate.
 6. An electronic device comprising: the light-emittingdevice according to claim 5; and any one of a microphone, a camera, anoperation button, an external connection portion, and a speaker.
 7. Anelectronic device comprising: the light-emitting device according toclaim 5; and a housing or a touch sensor.
 8. A lighting devicecomprising: the light-emitting device according to claim 5; and any oneof a housing, a cover, and a support.
 9. The light-emitting elementaccording to claim 4, wherein the host material has higher tripletexcitation energy than the guest material.
 10. The light-emittingelement according to claim 4, wherein the host material comprises an-electron deficient heteroaromatic compound.
 11. The light-emittingelement according to claim 4, wherein the host material comprises an-electron rich heteroaromatic compound.
 12. The light-emitting elementaccording to claim 4, wherein the host material comprises an aromaticamine compound.